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prof. Ing. Ondřej Jiříček, CSc.

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Are the mycelium-based diffusers applicable?

  • Department: Department of Physics
  • Annotation:
    The use of materials based on the mycelial growth on recycled materials is widely studied. The absorbent properties of such composites can be found in a number of articles. However, this one focuses on the possibility of using mycelium-based composites for the design of sound diffusers. Diffusion parameters were determined in the form of normalized and non-normalized diffusion coefficient in a free field according to ISO 17497-2. The measured results show that the use of mycelium for the construction of diffusers is promising. However, the results are not the best, which is due to the architectural design.

Comparisional study of sound power measurement from sound intensity and LDV

  • Department: Department of Physics
  • Annotation:
    The article presents preliminary study of sound power measurement using sound intensity and laser Doppler vibrometry.

Effect of soldiers on vibroacoustic alarm response in workers of subterranean termites (Blattodea: Rhinotermitidae)

  • DOI: 10.1007/s00040-023-00945-0
  • Link: https://doi.org/10.1007/s00040-023-00945-0
  • Department: Department of Physics
  • Annotation:
    Subterranean termites rely on chemical and vibroacoustic communication as they live enclosed in tunnels in the soil or wood. While social context is known to influence colony-level behaviors in many social insects, its influence on alarm communication remains unstudied. We tested the influence of the soldier caste on worker behavioral plasticity for subterranean termites: two species of Reticulitermes and Coptotermes formosanus. We altered the group composition according to soldier proportion or their replacement by chemical signals (hexane extracts). The responses of termites to stimuli known to provoke alarm responses, such as human breath simulating a breech in the nest or crushed soldier head (CSH) containing the chemical alarm cues, comprised increased movement and increased vibroacoustic alarm signaling. Species differed in the intensity of their responses, which were generally stronger in Reticulitermes. Groups of Reticulitermes with soldiers responded more strongly to CSH, while groups of R. virginicus only responded to human breath in the presence of soldier extracts. The responses of Coptotermes formosanus showed no effect of group composition on responses to stimuli, suggesting that soldier presence does not affect vibroacoustic behavior in this species. Our results highlight how alarm behavior changes quickly in closely related species as part of finely tuned behavioral mechanisms optimizing a species' response in each environment including in the presence of natural predators and competitors.

EXPERIMENTAL VALIDATION OF SEMIEMPIRICAL MODEL BASED ON ACOUSTIC RADIATION MATRIX METHOD

  • Department: Department of Physics
  • Annotation:
    Sound power determination using the surface velocity of the source has been a research interest for a long. While the theoretical foundation of this method is well-established in the literature the experimental validation of this method has still not yet been explored satisfactorily. To provide experimental support for this method and to discuss its limitations this work emphasizes on the experimental approach. In this work, a flat plate, vibrating in the air medium is studied for the determination of radiated sound power from a vibrating structure. To do so a semi-empirical model based on a radiation resistance matrix and source surface velocity is exploited. The radiation resistance matrix was calculated theoretically using two attributes of the source and medium say the geometry of the radiating source in this case a flat square plate and the density of the radiating medium respectively. On the other hand, another quantity required for the sound power determination namely the surface velocity was measured experimentally using laser scanning. Using this radiation matrix and surface velocity the radiated sound power was calculated and the obtained results were compared with the standard methods. Unlike the archived studies on this method, this work aims to implement this method for designing the appropriate measurement techniques for the acoustic performance of the large building envelopes having flexible façade.

Experimental verification of sound power determination methods based on radiation matrix.

  • Department: Department of Physics
  • Annotation:
    The theoretical foundation of sound power determination from a sound radiating surface using volume velocity and acoustic radiation matrix (ARM) is well established in the literature. However, a detailed experimental investigation of the accuracy of this method over a wide frequency band has not been presented. In this study, the ARM method is analyzed thoroughly to identify factors that can affect the accuracy of the calculated sound power. To do so the acoustic radiation matrix is observed closely as this is the main parameter responsible for determining the sound power. Further experiments were performed to calculate the sound power using the ARM method and results were compared to those obtained using the ISO 9614–2 and Rayleigh’s Integral Method (RIM). Comparison of these results in wide frequency bands provides insight into the acoustic radiation matrix based on the assumptions made during the modeling of the ARM method. These insights are then used to improve the model’s accuracy with the motivation to apply this method to the in-situ measurement of the large building facades.

From the history of Czech acoustics

  • Authors: prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Sborník 105. akustického semináře. Praha: Česká akustická společnost, 2024. p. 15-21. ISBN 978-80-01-07301-8.
  • Year: 2024
  • Department: Department of Physics
  • Annotation:
    This text was created as a Czech version of a lecture on the history of acoustics in the Czech lands in the twentieth century, delivered at the Forum Acusticum 2023 congress. However, it is not identical, as it was modified for the needs of the 105th acoustic seminar. The text is divided into three parts: the history of science and research in the field of acoustics, the development of the acoustic industry (mainly electroacoustics) and information about professional groups and societies.

Subjective evaluation of FSM sound using a pairwise comparison test

  • Department: Department of Physics
  • Annotation:
    Pairwise comparison methods are well-known methods used for subjective evaluation of various product sounds. The paper deals with usage of this method for evaluation of fuel supply modules.

Acoustics in the Czech Lands During the 20th Century

  • Authors: prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Forum Acusticum 2023. Madrid: European Acoustics Association, 2023. p. 3541-3544. ISSN 2221-3767. ISBN 978-88-88942-67-4.
  • Year: 2023
  • DOI: 10.61782/fa.2023.1171
  • Link: https://doi.org/10.61782/fa.2023.1171
  • Department: Department of Physics
  • Annotation:
    Above all, it must be said that during the 20th century, the Czech lands were part of various state arrangements, which influenced the development of all branches of science and industry. The development of acoustics already dates back to the turn of the nineteenth and twentieth centuries and is particularly associated with the name of Vincenc Strouhal, the author of studies on wires experiencing vortex shedding and singing in the wind. In the period between the wars, the main development of acoustics was connected with the creation of radio and cinematography. At that time, the first companies focused on electroacoustics were founded. The real development of acoustics came after the Second World War, despite being hampered by the existence of the Iron Curtain, when the exchange of information or equipment between West and East was very difficult. In addition to the creation of a number of state-owned enterprises for the development of radio, television, and machine diagnostics, this period is also characterized by active associational activity, which after 1989 came under the Czechoslovak or Czech Acoustic Society. The article summarizes the historical development of acoustics in the twentieth century both in the field of research and in the field of industry and practical applications.

Alarm communication predates eusociality in termites

  • DOI: 10.1038/s42003-023-04438-5
  • Link: https://doi.org/10.1038/s42003-023-04438-5
  • Department: Department of Physics
  • Annotation:
    Termites (Blattodea: Isoptera) have evolved specialized defensive strategies for colony protection. Alarm communication enables workers to escape threats while soldiers are recruited to the source of disturbance. Here, we study the vibroacoustic and chemical alarm communication in the wood roach Cryptocercus and in 20 termite species including seven of the nine termite families, all life-types, and all feeding and nesting habits. Our multidisciplinary approach shows that vibratory alarm signals represent an ethological synapomorphy of termites and Cryptocercus. In contrast, chemical alarms have evolved independently in several cockroach groups and at least twice in termites. Vibroacoustic alarm signaling patterns are the most complex in Neoisoptera, in which they are often combined with chemical signals. The alarm characters correlate to phylogenetic position, food type and hardness, foraging area size, and nesting habits. Overall, species of Neoisoptera have developed the most sophisticated communication system amongst termites, potentially contributing to their ecological success.

Sound and its quality

  • Department: Department of Physics
  • Annotation:
    The article reflects on the subjective perception of sounds. It focuses on the question of when sound is considered as a noise and about speech intelligibility.

First part of the psychoacoustic experiment with fuel supply modules

  • Department: Department of Physics
  • Annotation:
    This contribution is focused on the psychoacoustic evaluation of fuel supply module sound. It is a common automotive part producing a specific sound, which is subjectively evaluated as a first part of more complex psychoacoustic experiment. This experiment provides new information about the perception of this product sound and will lead to the development of a psychoacoustic model for the objective evaluation of the fuel supply module sound.

On the Determination of Acoustic Properties of Membrane Type Structural Skin Elements by Means of Surface Displacements

  • DOI: 10.3390/app112110357
  • Link: https://doi.org/10.3390/app112110357
  • Department: Department of Physics
  • Annotation:
    The article focuses on the determination of the acoustic properties (sound transmission loss, sound absorption and transmission coefficient under acoustic plane wave excitation) of membrane-type of specimens by means of a combination of incident plane wave sound pressure and membrane surface displacement information, measuring the sound pressure with a microphone and the membrane displacement by means of a laser Doppler vibrometer. An overview of known measurement methods and the theoretical background of the proposed so-called mobility-based method (MM) is presented. The proposed method was compared with the conventional methods for sound transmission loss and absorption measurement in the impedance tube, both numerically and experimentally. Finite element model (FEM) simulation results of two single layer membrane samples of different shape configurations were compared, amongst which six different variations of the backing wall termination. Four different approaches to determine the sound transmission loss and two methods to determine sound absorption properties of the membranes were compared. Subsequently, the proposed method was tested in a laboratory environment. The proposed MM method can be possibly used to measure the vibro-acoustic properties of building parts in situ.

Pre-test for sound quality evalutation of fuel supply modules

  • Department: Department of Physics
  • Annotation:
    This article is focused on the psychoacoustic evaluation of the sound produced by the fuel supply modules - common automotive products installed in the fuel tanks of automobiles with combustion engines, producing typical sound. It contains evaluation of several psychoacoustic metrics and description of the performed pre-test as a first part of more complex psychoacoustic experiment. This experiment will lead to the development of psychoacoustic model for objective evaluation of the fuel supply module sound, that could be used in product development processes in future.

A Comparison of Sharpness Evaluation Models

  • Department: Department of Physics
  • Annotation:
    In this paper, the psychoacoustic quantity of sharpness is discussed and three models which can objectively evaluate it. The motivation for this research is to compare several methods of sharpness evaluation and find the differences as it is difficult to say which is the best. The models that were proposed by Fastl, the German standard and the method from Musical Acoustics Research Centre (MARC) in Prague were tested for this paper. Different sounds including bandpass noise, traffic, speech and non-sinusoidal wave forms were tested on each model in MATLAB. Narrowband noises rose in sharpness at a faster rate than broadband noises. The MARC method returned higher values of sharpness than the Fastl method throughout while the German standard gave the highest sharpness at high frequency bands. The MARC method appeared to give results closer to the standard.Comparisons were made between the algorithms and variations discussed so that we can gain a deeper insight into psychoacoustics and sound quality.

Expectations of the acoustic environment in the national library of technology - Case study

  • DOI: 10.1016/j.apacoust.2020.107507
  • Link: https://doi.org/10.1016/j.apacoust.2020.107507
  • Department: Department of Physics
  • Annotation:
    The function of libraries has changed considerably in recent decades. This article presents the case study of the acoustic properties of the National Library of Technology (NTK), built in 2009, visited by more than 2000 users daily. From the acoustic point of view, these are coupled spaces, with horizontally structured spaces, which allow for dividing the space into zones according to the function of use. Through their openness, the individual floors can partially be viewed as open-space offices. Moreover, all floors are connected by a common central atrium, which is the cause of the mentioned acoustic coupling. Undesirable and annoying noise is one of the fundamental problems of these spaces. This article deals with the relationship between the number of visitors, noise in a given space and its acoustic parameters and the impact of these parameters on acoustic comfort, which is a compromise between RT, STI and noise. (C) 2020 Elsevier Ltd. All rights reserved.

Chemical and vibratory signals used in alarm communication in the termite Reticulitermes flavipes (Rhinotermitidae)

  • DOI: 10.1007/s00040-018-00682-9
  • Link: https://doi.org/10.1007/s00040-018-00682-9
  • Department: Department of Physics
  • Annotation:
    Termites have evolved diverse defence strategies to protect themselves against predators, including a complex alarm communication system based on vibroacoustic and/or chemical signals. In reaction to alarm signals, workers and other vulnerable castes flee away while soldiers, the specialized colony defenders, actively move toward the alarm source. In this study, we investigated the nature of alarm communication in the pest Reticulitermes flavipes. We found that workers and soldiers of R. flavipes respond to various danger stimuli using both vibroacoustic and chemical alarm signals. Among the danger stimuli, the blow of air triggered the strongest response, followed by crushed soldier head and light flash. The crushed soldier heads, which implied the alarm pheromone release, had the longest-lasting effect on the group behaviour, while the responses to other stimuli decreased quickly. We also found evidence of a positive feedback, as the release of alarm pheromones increased the vibratory communication among workers and soldiers. Our study demonstrates that alarm modalities are differentially expressed between castes, and that the response varies according to the nature of stimuli.

The influence of thermal insulation selection on a facade sound insulation property – theoretical case study

  • Department: Department of Physics
  • Annotation:
    Impact of the external thermal insulation composite system (ETICS) on the sound reduction index improvement is widely discussed topic. ETICSs are already several years commonly used to reduce buildings thermal loses. However, its application can negatively influence facades sound insulation properties. In the high frequency range an additional thermal insulating layer improves the sound insulation property. However, in the low frequency range the sound insulation spectra rather often decrease. This decrease is caused by a mass - spring - mass resonance of the ETICS system. Location and the depth of resonance dip depend on the ETICS composition. Several prediction models and measurement-based case studies were published already. In this contribution, an analytical model is used to predict the sound reduction index, using a measured dynamic stiffness of the ETICS system. A number of different thermal insulating layers are analysed having similar thermal properties but different material dynamic stiffnesses and loss factors. The comparison of theoretically predicted sound insulation spectra and the impact of the dynamic stiffness measurement technique are presented.

Spherical sound sources localization using SONAH

  • Authors: Hung-Jr, Ch., Koutný, A., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of the Inter-Noise 2018. Washington, DC: Institute of Noise Control Engineering of the USA, 2018. p. 1-10. ISSN 0736-2935.
  • Year: 2018
  • Department: Department of Physics
  • Annotation:
    Near Field Acoustical Holography (NAH) is a practical tool for noise source identification and sound field visualization. Statistically Optimized Near Field Acoustical Holography (SONAH) is developed in recent years due to its patch reconstruction ability, enabling smaller measurement aperture and shorter measurement time. In this paper, SONAH is adopted to localize the spherical sound sources positions. Firstly, three spherical sound sources are placed at the baffled source plane. Then, the sound pressure at the holographic plane is synthesized using the spherical sound sources propagation formula. After that, the synthesized pressure data are used as input to SONAH to localize all sources positions. Truncated singular value decomposition (TSVD) regularization is utilized in the SONAH reconstruction process to stabilize the solution. The SONAH reconstruction results are compared with the synthesized pressure very close to the source plane using the same spherical sound sources propagation formula. The comparison demonstrates accurate localization capability of SONAH algorithm. In addition, the difference between the reconstruction pressure amplitude by SONAH and the synthesized pressure by the spherical sound sources propagation formula is also discussed in this study.

Piezoelectric line moment actuator for active radiation control from light-weight structures

  • DOI: 10.1016/j.ymssp.2017.04.003
  • Link: https://doi.org/10.1016/j.ymssp.2017.04.003
  • Department: Department of Physics
  • Annotation:
    This article outlines the design of a piezoelectric line moment actuator used for active structural acoustic control. Actuators produce a dynamic bending moment that appears in the controlled structure resulting from the inertial forces when the attached piezoelectric stripe actuators start to oscillate. The article provides a detailed theoretical analysis necessary for the practical realization of these actuators, including considerations concerning their placement, a crucial factor in the overall system performance. Approximate formulas describing the dependency of the moment amplitude on the frequency and the required electric voltage are derived. Recommendations applicable for the system's design based on both theoretical and empirical results are provided. (C) 2017 Elsevier Ltd. All rights reserved.

Source distance determination based on the spherical harmonics

  • DOI: 10.1016/j.ymssp.2016.09.015
  • Link: https://doi.org/10.1016/j.ymssp.2016.09.015
  • Department: Department of Physics
  • Annotation:
    This paper deals with the processing of signals measured by a spherical microphone array, focusing on the utilization of near-field information of such an array. The processing, based on the spherical harmonics decomposition, is performed in order to investigate the radial-dependent spherical functions and extract their argument – distance to the source. Using the low-frequency approximation of these functions, the source distance is explicitly expressed. The source distance is also determined from the original equation (using no approximation) by comparing both sides of this equation. The applicability of both methods is first presented in the noise-less data simulation, then validated with data contaminated by the additive white noise of different signal-to-noise ratios. Finally, both methods are tested for real data measured by a rigid spherical microphone array of radius 0.15 m, consisting of 36 microphones for a point source represented by a small speaker. The possibility of determination of the source distance using low-order spherical harmonics is shown.

Aeroacoustics research in Europe: The CEAS-ASC report on 2015 highlights

  • DOI: 10.1016/j.jsv.2016.06.029
  • Link: https://doi.org/10.1016/j.jsv.2016.06.029
  • Department: Department of Physics
  • Annotation:
    The Council of European Aerospace Societies (CEAS) Aeroacoustics Specialists Committee (ASC) supports and promotes the interests of the scientific and industrial aeroacoustics community on the European scale, and European aeronautics activities internationally. Each year, the committee highlights several of the research and development projects in Europe. This paper is the 2015 issue of this collection of Aeroacoustic Highlights, compiled from contributions submitted to the CEAS-ASC.

Listening pre-test of computer keyboard sound

  • Department: Department of Physics
  • Annotation:
    This paper describes the preliminary trial of computer keyboards sounds as the first acquaintance with the psychoacoustic listening test. The description of preparation, process and evaluation is presented as well.

Monaural objective parameters for quality prerformance evaluation of enclosed space

  • Authors: Simon, O., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: 93. akustický seminář. Praha: Česká akustická společnost, 2016. pp. 39-44. ISBN 978-80-01-06025-4.
  • Year: 2016
  • Department: Department of Physics
  • Annotation:
    This article deals with a summary of monaural objective acoustical parameters of closed spaces. Every parameter is introduced with its mathematical definition and its subjective meaning for the audience. Also, recommended values of the parameters for concert and multipurpose halls referring to various sources are presented.

Comparison of force and moment behavior of bimorph actuator

  • DOI: 10.13140/RG.2.1.3864.8800
  • Link: https://doi.org/10.13140/RG.2.1.3864.8800
  • Department: Department of Physics
  • Annotation:
    This paper deals with an actuator based on piezoelectric bimorphs developed at CTU for applica- tions of ASAC on thin structures. The actuator takes the form of two pairs of bimorphs connected separately, so that the actuator can act in both moment and force configurations simultaneously. The ASAC system using this actuator was tested on a simple structure in the form of a steel strip fixed at both ends. The behavior of the actuator was compared with theoretical assumptions including efficiency of the actuator as a function of the position and power input. A good agreement has been demonstrated between the model results and the measurement.

Complex alarm strategy in the most basal termite species

  • DOI: 10.1007/s00265-015-2007-9
  • Link: https://doi.org/10.1007/s00265-015-2007-9
  • Department: Department of Physics
  • Annotation:
    Studying basal taxa often allows shedding a light on the evolution of advanced representatives. The most basal termite species, Mastotermes darwiniensis, possesses unique morphological and behavioural traits, of which many remain scarcely studied. For these reasons, we conducted a comprehensive study of the alarm communication in this species and compared its components to behavioural modes described in other termites. In M. darwiniensis, the alarm is communicated by substrate-borne vibrations resulting from vertical vibratory movements. Another similar behaviour consists in longitudinal movements, by which the alarm is delivered to other termites in contact with alerted individual. Both these two behavioural modes could be used in synergy to create complex movements. M. darwiniensis also uses chemical alarm signals produced by labial gland secretion, in contrast to Neoisoptera in which this function is fulfilled exclusively by the frontal gland secretion. Moreover, we demonstrated in M. darwiniensis the presence of a positive feedback mechanism thought to occur exclusively in the crown group Termitidae. This positive feedback consists in both oscillatory movements of alerted individuals in response to alarm signals and release of alarm pheromone by excited soldiers. Our results confirm that M. darwiniensis is a remarkable example of mosaic evolution, as it combines many primitive and advanced features, and its alarm communication clearly belongs to the latter category.

Measurement of behavior of a force-moment actuator in general working mode

  • DOI: 10.13140/RG.2.1.2603.3120
  • Link: https://doi.org/10.13140/RG.2.1.2603.3120
  • Department: Department of Physics
  • Annotation:
    The present paper deals with the testing of a force-moment bimorph actuator designed for ASAC applications. The actuator was tested on the third natural mode of a steel strip fixed on both ends baffled in the rigid board. The strip was excited by a point force in its center at a frequency corresponding to the third mode. The presented results show the efficiency of the actuator as a function of the actuator’s working mode. Measurements were realized in an anechoic room to simplify measurement of the radiated sound field. The resulting efficiency was evaluated by means of sound pressure in the position of microphone 0.5 m above the strip. The behavior of the force moment actuator in general working mode is discussed.

Pneu-acoustic actuator with variable waveguide

  • Department: Department of Physics
  • Annotation:
    The paper describes properties of the pneu-acoustic transducer with variable waveguide. Basic principles of its function and influence of the waveguide length are described and evaluated. Analysis of the transient after opening of the valve is studied using wavelet transform.

The nature of alarm communication in Constrictotermes cyphergaster (Blattodea: Termitoidea: Termitidae): the integration of chemical and vibroacoustic signals

  • DOI: 10.1242/bio.014084
  • Link: https://doi.org/10.1242/bio.014084
  • Department: Department of Physics
  • Annotation:
    Alarm signalling is of paramount importance to communication in all social insects. In termites, vibroacoustic and chemical alarm signalling are bound to operate synergistically but have never been studied simultaneously in a single species. Here, we inspected the functional significance of both communication channels in Constrictotermes cyphergaster (Termitidae: Nasutitermitinae), confirming the hypothesis that these are not exclusive, but rather complementary processes. In natural situations, the alarm predominantly attracts soldiers, which actively search for the source of a disturbance. Laboratory testing revealed that the frontal gland of soldiers produces a rich mixture of terpenoid compounds including an alarm pheromone. Extensive testing led to identification of the alarm pheromone being composed of abundant monoterpene hydrocarbons (1S)-α-pinene and myrcene, along with a minor component, (E)-β-ocimene. The vibratory alarm signalling consists of vibratory movements evidenced as bursts; a series of beats produced predominantly by soldiers. Exposing termite groups to various mixtures containing the alarm pheromone (crushed soldier heads, frontal gland extracts, mixture of all monoterpenes, and the alarm pheromone mixture made of standards) resulted in significantly higher activity in the tested groups and also increased intensity of the vibratory alarm communication, with the responses clearly dose-dependent. Lower doses of the pheromone provoked higher numbers of vibratory signals compared to higher doses. Higher doses induced long-term running of all termites without stops necessary to perform vibratory behaviour. Surprisingly, even crushed worker heads led to low (but significant) increases in the alarm responses, suggesting that other unknown compound in the worker’s headis perceived and answered by termites. Our results demonstrate the existence of different alarm levels in termites.

A Brief Comparison of Loudness Evaluation Models

  • Department: Department of Physics
  • Annotation:
    In this paper, the concept of psychoacoustic loudness is discussed and in particular, objective methods for its evaluation.Two prominent methods are considered; the method proposed by Zwicker and the method proposed by Moore and Glasberg. Algorithms for each method are implemented in MATLAB in order to evaluate loudness for a variety of stimuli including pure tones, bandpass noise and industrial noise. Quantifiable differences are observed in the outputs of the two methods and the possible causes of these differences are discussed.

Characteristics of pneu-acoustic actuator

  • Department: Department of Physics
  • Annotation:
    The paper describes acoustic properties of the pneu-acoustic transducers. Basic acoustic parameters as a sensitivity, frequency response and directivity were evaluated. The simple model of the finite conical horn based on Webster's equation is presented as well.

Combined force-moment actuator for ASAC

  • DOI: 10.13140/2.1.3619.4888
  • Link: https://doi.org/10.13140/2.1.3619.4888
  • Department: Department of Physics
  • Annotation:
    This paper deals with a recently developed actuator based on piezoelectric bimorphs which are useful for ASAC applications. The actuator takes the form of two channels with pairs of bimorphs. Each of the bimorph transducers in the couple is connected separately so that the actuator can act in both moment and force configurations simultaneously. The control algorithm allows the ratio between the moment and force excitation to be adapted according to the desired mechanical output. The ASAC system using this actuator was tested on a simple structure in the form of a fixed beam. Configurations with maximum attenuation were selected and discussed.

Experience with measurement of diffusion coefficient in a free field

  • DOI: 10.13140/2.1.1753.5367
  • Link: https://doi.org/10.13140/2.1.1753.5367
  • Department: Department of Physics
  • Annotation:
    The acoustic behavior of diffusers is usually described by three parameters: sound absorption co-efficient, scattering coefficient and diffusion coefficient. The first two coefficients are measured in a reverberation room and have been standardized for many years. This contribution deals with the measurement of the diffusion coefficient of surfaces in an anechoic room characterizing the directional uniformity of the sound scattering. The diffusion coefficient is defined in ISO 17497-2 issued in 2012. The measurement technique was tested on an MLS diffuser of the 4th order. Measured results were in good conformity with theoretical assumptions.

Active Structural Acoustic Control on Double-Layer Acoustic Panel

  • Department: Department of Physics
  • Annotation:
    The paper deals with active structural acoustics control (ASAC) applied to the lightweight structure in order to increase transmission loss at low frequencies. Presented results show efficiency of moment actuators developed especially for ASAC mounted on a double-layer acoustic panel consisting of two metal sheets separated by air gap.

Broadband active structural acoustic control with moment actuator

  • Department: Department of Physics
  • Annotation:
    Sufficient transmission loss of lightweight structures is always a challenge, especially at low frequencies. The paper deals with application of the moment actuator developed at CTU specifically for active structural acoustic control (ASAC) to the double-layer structure consisting of two metal sheets separated by an air gap. The efficiency of the actuators and the entire system were experimentally tested using various noise signals, particularly low-frequency broadband noise. A comparison of results obtained from application of actuators to the incident plate and to the radiating plate of the double layer structure is presented. The filtered-x LMS algorithm was used in the experimental part of ASAC with promising results in the frequency range from 60 Hz to 200 Hz.

Holographic reconstruction of an incident field assuming the spherical waves scattered by a rigid sphere

  • Authors: Koutný, A., prof. Ing. Ondřej Jiříček, CSc., Thomas, J.-H.
  • Publication: Proceedings of Inter-noise 2013. Vienna: Austrian Noise Abatement Association, 2013. ISBN 978-1-63266-267-5.
  • Year: 2013
  • Department: Department of Physics
  • Annotation:
    This paper deals with the reconstruction of an acoustic field in the near-field around a rigid sphere using Near-field Acoustical Holography (NAH) based on an expansion in terms of the spherical harmonics. By employing the rigid sphere providing stable inversion of the propagation function one has to take into account the scattering effect that could significantly affect the total field around the sphere. This effect is commonly accounted for the separation of the incident and scattered field from the total measured field. In applications performing sound field reconstruction by NAH, the presence of source in the near-field of the sphere is to be expected. In this study, such a source in the near-field is considered and a method for determination of the source distance is examined. We consider the spherical waves scattered by a rigid spherical surface for the separation and subsequent reconstruction of the only incident field in this paper. The results are presented in a model simulation.

Measurement of diffusion coefficient in free field

  • Department: Department of Physics
  • Annotation:
    This paper deals with the measurement of the diffusion coefficient of surfaces in anechoic room characterizing the directional uniformity of the sound scattering. The diffusion coefficient is defined in ISO 17497-2. Measurement technique was tested on MLS diffuser of 4th order. Measured results were in good conformity with theoretical assumptions.

Application of moment actuator in systems of active control of transmission loss of double panel

  • Department: Department of Physics
  • Annotation:
    One of the dominant research areas in the field of active structural acoustics control (ASAC) is improvement of transmission loss in lightweight structures. The present paper deals with the application of the moment actuator developed for ASAC on a double-panel structure consisting of two metal sheets separated by an air gap. The first experiments show promising results in the frequency range from 60 Hz to 150 Hz.

Dual channel feed-forward active structural acoustic control of test mock-up

  • Department: Department of Physics
  • Annotation:
    The paper describes the design, system arrangement, and results evaluation of a dual- channel feed-forward ASAC experiment. As a testing structure, a three dimensional mock-up (machinery casing) excited by polyharmonic signal was used. Sound pressure level measured by two error microphones was employed as an error criterion. The overall system performance was evaluated by means of the total radiated power measured by intensity scanning. Finally, the results are discussed in detail.

Monaural and binaural parameters of Rudolfinum concert halls in Prague

  • DOI: 10.1016/j.apacoust.2012.03.014
  • Link: https://doi.org/10.1016/j.apacoust.2012.03.014
  • Department: Department of Physics
  • Annotation:
    Objective parameters for the evaluation of the Rudolfinum concert hall in Prague, Czech Republic are the focus of the present article. The measured results for Reverberation parameters, Energy parameters, Intelligibility parameters, and Spatial parameters of the building's two halls are presented and discussed including a comparison with recommended values or theory, as well as several unique architectural and acoustical qualities of the halls. The early lateral energy fraction parameter is measured by the intensity probe method discussed in the supplement. The performance is verified by tests in anechoic and reverberant rooms.

Reconstruction of normal surface velocity from measurement of acoustically induced vibration of a thin membrane

  • Department: Department of Physics
  • Annotation:
    This paper deals with the theoretical study of extension of the laser scanning vibrometer measurement for reconstruction of acoustic quantities by Nearfield Acoustical Holography (NAH). This approach could be applied in a situation where the direct measurement of source vibration is complicated or impossible. A thin rectangular membrane with reflective coating is inserted in the near field of the source and its normal velocity is measured by a laser scanning vibrometer. Using a model equation considering acoustically induced vibration of the membrane, the original sound field radiated by the source is calculated and used for reconstruction of the normal source velocity. The presented paper presents preliminary theoretical results obtained in a mathematical model of the real situation.

Active structural acoustic control of thin plate with mixed boundary conditions

  • Department: Department of Physics
  • Annotation:
    The paper deals with active structural acoustic control of the experimental mock-up (baffled thin plate with mixed boundary conditions). The aim of the experiment is to globally reduce radiated sound pressure level by actions of distributed forces and line moments used as secondary actuators.

Application of modified SONAH to velocity reconstruction of experimental mock-up

  • Authors: Koutný, A., Švec, P., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Inter-noise 2011. Kyoto: Acoustical Society of Japan, 2011. ISSN 0105-175X.
  • Year: 2011
  • Department: Department of Physics
  • Annotation:
    The paper deals with application of modified Statistically Optimized Near-field Acoustic Holography (SONAH) to reconstruction of normal velocity on the source surface.

Near-field Acoustic Holography Based on Combined Elementary Wave Model

  • Authors: Koutný, A., Švec, P., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Forum Acusticum 2011. Madrid: European Acoustics Association, 2011. pp. 2861-2864. Danish Acoustical Society. ISSN 2221-3767. ISBN 978-84-694-1520-7.
  • Year: 2011
  • Department: Department of Physics
  • Annotation:
    The paper deals with reconstruction of sound field sources distribution using Near-field Acoustic Holography (NAH) based on elementary wave models. In our approach we decide to use combination of planar (SONAH) cylindrical or spherical (HELS) waves models according to frequency and measured aperture size.

Near-field acoustic holography based on combined wave function model

  • Department: Department of Physics
  • Annotation:
    Paper deals with reconstruction of sound field sources distribution using Near-fiels Acoustic Holography (NAH) based on elementary wave models.

Non-equidistant k-space sampling in statistically optimized near-field acoustic holography

  • Department: Department of Physics
  • Annotation:
    The paper deals with an effect of a non-equidistant (non-linear) k-space sampling to the particle velocity field reconstructed by the statistically optimized near-field acoustic holography (SONAH).

Comparison of Near-field Acoustic Holography Regularization Methods

  • Authors: Koutný, A., Švec, P., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of EUROREGIO 2010. Ljubljana: Slovenian Acoustical Society, 2010. ISBN 978-961-269-283-4.
  • Year: 2010
  • Department: Department of Physics
  • Annotation:
    The paper compares different regularization techniques for ill-posed inverse problems like near-field acoustical holography (NAH). Experiments with simple planar source excited by mechanical force(s) were performed and velocity distribution of the vibrating plate was reconstructed by means of NAH from measured complex pressures. Special attention is aimed to patch holography algorithms (especially SONAH) allowing to measure only small portion of a real source and providing reconstruction on part of a source beneath the measured surface.

Methods for the Assessment of Pleasantness in Sound Quality

  • DOI: 10.3397/1.3270100
  • Link: https://doi.org/10.3397/1.3270100
  • Department: Department of Physics
  • Annotation:
    Recently, listener tests of certain products have shown that the sense of pleasantness is significant in sound quality evaluation. For instance, pleasantness was an attribute frequently selected by subjects in the free word description of vacuum cleaner sounds. However, the relationship between the sense of pleasantness and psychoacoustic metrics is specific for each product. Present predicting models of pleasantness are not always suitable and have certain limitations, hence a new model of pleasantness was developed in our research. The development was based on the evaluation of specific products (vacuum cleaners and computer fans). The new model was then applied in two cases: first, for the evaluation of vacuum cleaners, which strongly correlated with the psychoacoustic metrics. Equally, the new model can be applied to a product for which the correlation coefficients between the standard psychoacoustic metrics and pleasantness were not significant.

Study of capabilities of moment actuators in ASAC

  • Department: Department of Physics
  • Annotation:
    For suppression of radiated power various kinds of secondary actuators as shakers, piezoelectric stacks or smart materials can be used. In addition to the force actuators moment actuators can be applied. Piezoceramics based line moment actuators are used in presented experiments. Sound radiation of simple two-dimensional vibrating structure excited by mechanical force(s) is controlled by the moment actuators minimizing radiated power. Description of moment actuator as well as tested structure and achieved experimental results are presented.

Active control of sound transmission using moment actuators

  • Department: Department of Physics
  • Annotation:
    The paper deals with strategies of active structural acoustic control, method intensively developed within the last decade. Special interest is dedicated to the sound transmission through thin plate (wall). As the secondary control source moment actuators are selected. Active control is focused on control of radiating modes of the plate.

Comparison of sound absorption measurement methods

  • Department: Department of Physics
  • Annotation:
    The paper deals with comparison of two sound absorption measurement methods: handheld p-u probe method and standard Kundt's tube measurement. The p-u probe method represents relatively new and unverified approach for which practical employment repeatability and reliability tests are needed.

Experiments with active control of sound radiation from vibrating plates

  • Department: Department of Physics
  • Annotation:
    The paper deals with particular problems of active structural acoustic control of thin plates. As primary excitation, force and incident sound wave was used. The active control system was tested with secondary actuators producing force and line moment.

In situ sound absorption measurement in car interior

  • Department: Department of Physics
  • Annotation:
    The paper deals with in situ measurement of sound absorption in small enclosures, e.g. car interior. The handheld device based on p-u intensity sensor was tested. Basic characteristics of the method with respect to its practical usage were examined. Various types of surfaces were measured and results were compared with other measurement approaches. Applicability of the new method was discussed.

Sound intensity p-u probe for measurement of acoustic impedance

  • Authors: Koutný, A., prof. Ing. Ondřej Jiříček, CSc., Švec, P.
  • Publication: Sborník 79. akustického semináře. Praha: Česká akustická společnost, 2009. pp. 5-16. ISBN 978-80-01-04427-8.
  • Year: 2009
  • Department: Department of Physics
  • Annotation:
    The paper deals with measurement of acoustic impedance and absorption coefficient using p-u intensity probe produced by Microflown Technologies. Basic characteristics of th eprobe are briefly presented and its principle explained.

Acoustic research at Department of Physics

  • Department: Department of Physics
  • Annotation:
    The paper describes history of acoustic research at the Department of Physics from its foundation after second world war till present days.

Active Control of Sound Radiation from Vibrating Bodies Using Piezoelectric Actuators

  • Department: Department of Physics
  • Annotation:
    The paper deals with Active Control of Sound Radiation from Vibrating Bodies Using Piezoelectric Actuators

Active structural acoustic control of thin plate actuated by airborne noise

  • Department: Department of Physics
  • Annotation:
    This paper deals with the active structural acoustics control (ASAC) of a thin planar structure vibrating due to an incident sound wave.

History of Department of Physics of FEE CTU

  • Department: Department of Physics
  • Annotation:
    Paper describes all history of Department of Physics of FEE CTU in Prugue from its foundation to today.

Studies of capability of PZT actuators in ASAC

  • Department: Department of Physics
  • Annotation:
    This paper deals with the influence of the active structural acoustics control (ASAC) system configuration on the radiation of sound from a vibrating surface.

Choice of Auditory Attributes for Evaluation of Product Sound Quality

  • Authors: Jurč, R., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Inter-Noise 2006. Washington, DC: Institute of Noise Control Engineering of the USA, 2006.
  • Year: 2006
  • Department: Department of Physics
  • Annotation:
    The choice of auditory attributes is the first task to be considered at the beginning of sound quality evaluation. In addition, the following procedure of sound quality evaluation is based on these chosen attributes. Therefore, the choice of attributes has to be carefully and correctly performed. Two basic methods can be used for the choice of attributes, which are described in this paper. Next, the choice of attributes of sounds of vacuum cleaners and switched reluctance machines is included.

Design of cell for active structural acoutics control

  • Department: Department of Physics
  • Annotation:
    The paper deals with the design of cell for active structural acoustics control.

Next Investigation of Loudness Influence on the Pleasantness of Some Products

  • Department: Department of Physics
  • Annotation:
    Specific Loudness, as a distribution of loudness with the respect to critical bands, is important in the investigation of the influence of loudness on pleasantness. In this paper, the loudness spectra of each evaluated product are compared.

Research at the Department of Physics of the FEE CTU

Weak Radiating Cell for Active Vibration Control: First Approach

  • Department: Department of Physics
  • Annotation:
    Active control of noise and vibration is a technique suitable mainly for low frequencies for which passive methods are usually inefficient. The approach presented in this paper is based on elementary sources (cells) that change the sound radiation of a structure to the far field by active modification of structure vibrations. The elementary cell uses piezoelectric bending actuators to actuate vibrations of the secondary (active) surface of the cell. Both theoretical and experimental results are presented.

Differences in Influence of Loudness on Sense of Pleasantness

  • Authors: Jurč, R., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Inter-Noise 2005. Rio de Janeiro: Brazilian Acoustical Society, 2005. p. 1-6.
  • Year: 2005
  • Department: Department of Physics
  • Annotation:
    The sound of the each product has the specific features. Therefore, the product sound quality calls for the specific methods of the evaluation. The several subjective tests were performed in previous research. In these tests, the sounds of several devices (vacuum cleaners, computer fans and hair dryers) are evaluated. However, these subjective tests show the differences of the evaluation among the tested devices. The structure of sounds significantly affects the evaluation of human subjects.

Differences of Sound Quality Evaluations of Vacuum Cleaners, Computer Fans and Hair Dryers

  • Authors: Jurč, R., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Forum Acusticum 2005 Budapest. Budapest: OPAKFI Tudomanyos Egyesulet, 2005. p. 165-168. ISSN 0167-6393. ISBN 963-8241-68-3.
  • Year: 2005
  • Department: Department of Physics
  • Annotation:
    The aim of this paper is the investigation of the dependence between the specific features of structure of each evaluated devices and the values of the auditory characteristics. Two auditory characteristics, pleasantness and general impression, were shared by each evaluated device. The relationship between two auditory characteristics and the physical features is presented in this paper and differences in physical features are also described. Eventually, the values of the pleasantness and general impression will be compared with Zwicker's formula of psychoacoustic annoyance. Psychoacoustics metrics are significant for sound quality evaluation, they help compare the test results with the physical features. Similarly, loudness spectra help compare the specific features of sound structure with the values of the auditory characteristics.

Influence of Pleasantness on the General Impression of Tested Sounds

  • Authors: Jurč, R., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Workshop 2005. Praha: České vysoké učení technické v Praze, 2005. ISBN 80-01-03201-9.
  • Year: 2005
  • Department: Department of Physics
  • Annotation:
    Many factors (e.g. sound, colour, appearance of product etc.) influence the overall quality of a certain product. Sound quality, as a highly important component of the overall quality, is related to human perceptual reaction to the sound of a product. In this research, the products' sound quality is investigated. The aim of this contribution is to investigate the dependence between the sense of pleasantness and the sense of general impression for the evaluated sounds.

Secondary Sound Field Around Cylindrical Obstacle

  • Department: Department of Physics
  • Annotation:
    Secondary sound field is created around an obstacle when incidental wave is scattered and diffracted on the obstacle. Having the description of such a secondary sound field is important from technical point of view. For example measuring microphone, which has a cylindrical shape, affects an acoustical field that is measured. Because of this affection we can, for example, consider correction coefficients which can correct a value measured. We would like to propose different possibilities to obtain a description of secondary sound field around a cylindrical obstacle and prepare them for future usage.

The Comparison of Two Configurations of Secondary Sources ANC System in the Headrest of the Seat

  • Department: Department of Physics
  • Annotation:
    The paper deals with the comparison of two configurations of secondary sources ANC system in the headrest of the seat.

Description of Secondary Sound Field Around a Spherical Obstacle

Experimental Method for Measuring Secondary Sound Field for Sphere and Its Comparison with Analytical Results

  • Department: Department of Physics
  • Annotation:
    The development of a measuring method to serve as the basis for a numerical description of secondary sound fields affected by inserted bodies has been considered. Experiments were performed in an anechoic chamber, which is the model of a free field. For testing of the measuring methods, models of rigid sphere-shaped bodies were used. The mathematical model of a received secondary sound field is presently under development. The comparrison with analytical model is also planed.

Model Order Selection Using Penalty Criteria and Bayesian Evidence

Psychoacoustic and Objective Testing of Product Sound

  • Authors: Jurč, R., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Inter-Noise 2004. Praha: Česká akustická společnost, 2004. ISBN 80-01-03055-5.
  • Year: 2004
  • Department: Department of Physics
  • Annotation:
    This paper will present the results of several subjective tests. In these tests, the sounds of several devices (vacuum cleaners, computer fans and hair dryers) are investigated, with some tests verifying the previous tests. The aim of this paper is to determine the dependence between physical features and the judged characteristics of evaluated sounds. The semantic differential test was used in this research. The results were processed by use of statistical methods (multiple linear regression, correlation coefficient, etc.).

Scattering and Diffraction of Acoustical Waves on Sphere

Secondary Acoustical Field Around Spherical Obstacle

  • Department: Department of Physics
  • Annotation:
    We are preparing a method for creating mathematical models of a secondary sound field for different shaped bodies. For preparation of this method, a spherical body was chosen because the comparison between experimental and analytical results is feasible. A concave spherical body made of glass was used for our experiments. Measurements were performed in an anechoic room, which is the model of a free field. The obtained numerical description of secondary sound field was compared to description calculated on the basis of analytical formula. A mathematical model of the secondary sound field measured is being prepared, and measurements with differently shaped bodies and their mathematical models with respect to our experiences obtained up to now will be prepared.

Application of Local ANC in Passanger Seat

Comparison of Two Secondary Sources Configurations for Active Headrest

Diffraction on Circular Hard Board

  • Department: Department of Physics
  • Annotation:
    The paper deals with a method for measurement usually used for wind turbine noise. Some modifications of the measurement suggested in International Standard IEC 61 400-11 (Wind turbine generator systems - Part 11: Acoustic noise measurement techniques) were tested. For example, different microphone positions on a board and different mountings of a board were realized. Experiments were performed in an anechoic chamber, which is the model of a free field. The influence of scattering and diffraction on measurement was discussed. The results thus obtained were compared with the results reached by the standard measurement method, and the advantages and disadvantages were reviewed. In conclusion, an optimal measurement configuration was proposed.

Experiments with local active noise control in passenger seat

  • Department: Department of Physics
  • Annotation:
    Článek prezentuje praktické výsledky lokálního snižování hluku.

Implementation of IIR Filters in ANC Controllers

Improving of Measuring Method Using Hard Board

  • Department: Department of Physics
  • Annotation:
    Publikovaná práce pojednává o metodě měření, která je obvykle užívána pro měření hluku větrné turbíny. Byly testovány některé modifikace metody měření navrhované v mezinárodním standardu IEC 61 400-11 (Wind turbine generator systems - Part 11: Acoustic noise measurement techniques). Například byla provedena měření pro různé polohy umístění mikrofonu na desce. Měření byla prováděna v bezodrazové komoře, která je modelem volného pole. Byl diskutován vliv ohybu a rozptylu na výsledky měření a dále výhody a nevýhody daného způsobu měření.

Signal Processing of Time - Depending Signals of Periodically Working Machines

  • Department: Department of Physics
  • Annotation:
    Signals of periodically working machines, which were measured, were processed by classical methods of signal processing - Short Time Fourier Transform and Wavelet transform, and by a new method - Order Tracking Analysis. Some characteristics of processed signals and their physical interpretation has been surged. Psychoacoustical tests are in preparation; psychoacoustical indexes will be obtained by usual statistical method. On their basic the suppressions of the most disturbing frequencies will be suggested to improve acoustical properties of tested machines.

Subjective Testing of Computer Fan

  • Authors: Jurč, R., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: 67. Akustický seminář. Praha: Česká akustická společnost, 2003. pp. 7-14. ISBN 80-01-02850-X.
  • Year: 2003
  • Department: Department of Physics
  • Annotation:
    Presented in this paper are the results of sound testing of computer fans. The entire procedure of sound computer testing is explained. First, the procedure of processing the test results and the statistical method are described. The second part deals with the method of evaluating sound quality and the subjective test. The aim of this paper was to search for a dependence between the results of the subjective test and psychoacoustical metrics (loudness, sharpness roughness). Finally, the results of the subjective test are presented.

Theory of Scattering and Diffraction in Acoustics

  • Department: Department of Physics
  • Annotation:
    The scattering and diffraction are fenomenons which can affect resultes of acoustical measurement much. For correctins of measuring resultes the describtion of created secondary sound field is necessery. Lord Rayleigh has published the analytical solution for a sphere and the approximate solutin for a cilinder. For other shaped bodies the analytical solution do not exist. Many autors studied scattering and diffraction experimentally. In this paper published resultes are summerised. Presented study will be used for the preparation of mathematical model of secondary sound field for different shaped bodies.

Anechoic room for acoustics

  • Department: Department of Physics
  • Annotation:
    Paper describes konstruction and parameters of anechoic room located at CTU in Prague

Anechoic Room for Acoustics

Application of IIR Filters in Multi-channel ANC in Duct

  • Department: Department of Physics
  • Annotation:
    Článek popisuje použití IIR filtrů v řícicím členu ANC.

Creation of zones of quiet around artificial head

  • Department: Department of Physics
  • Annotation:
    Paper describes method of formation of zones of quiet aroudn artificial head.

Formating of zones of quiet around a head simulator

  • Department: Department of Physics
  • Annotation:
    Článek popisuje experimenty s lokálním ANC umístěným do podhlavníku sedačky.

Four-channel active noise control in an air-conditioning duct

  • Department: Department of Physics
  • Annotation:
    Článek pojednává o využití IIR filtrů ve čtyřkanálovém ANC systém v potrubí.

Psychoacoustic Basis of Sound Quality Evaluation in Cars

  • Authors: Kynčl, L., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Workshop 2002. Praha: České vysoké učení technické v Praze, 2002. pp. 166-167. ISBN 80-01-02511-X.
  • Year: 2002

The Use of Binaural Sound Recordings for Evaluation of Sound Quality

  • Authors: Kynčl, L., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Workshop 2002. Praha: Czech Technical University in Prague, 2002. p. 162-163. ISBN 80-01-02511-X.
  • Year: 2002

Usage of IIR filters for multi-channel ANC in a duct

  • Department: Department of Physics
  • Annotation:
    Paper describes practical experiences with usage of IIR filters

Active Improvement of Vehicle Interior Sound

  • Authors: prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Workshop 2001. Praha: České vysoké učení technické v Praze, 2001. pp. 96-97. ISBN 80-01-02335-4.
  • Year: 2001
  • Department: Department of Physics
  • Annotation:
    Článek popisuje možnosti ANC pro zlepšení vnitřního hluku vozidel

Application of Multi-channel Feed-forward Active Control in a Duct

Error and Feedback Paths Modeling using IIR Filters in ANC

Experiments with IIR models for active noise control in a duct

  • Department: Department of Physics
  • Annotation:
    Paper describes identification method for IIR modeling in ANC

Identification of Secondary and Feedback Paths in ANC

  • Department: Department of Physics
  • Annotation:
    Článek se zabývá identifikací a realizací sekundárních a zpětnovazebních cest v systému aktivního snižování hluku.

Psychoacoustic Product Sound Quality Evaluation

  • Authors: Kynčl, L., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: 17th International Congress on Acoustics IV. Rome: 17th International Congress on Acoustics, 2001. pp. 18-19. ISBN 88-88387-03-X.
  • Year: 2001
  • Department: Department of Physics
  • Annotation:
    Článek se zabývá metodami psychoakustického hodnocení reálních výrobků.

Sound Quality Methods in Cars

  • Authors: Kynčl, L., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of Workshop 2001. Praha: České vysoké učení technické v Praze, 2001. pp. 94-95. ISBN 80-01-02335-4.
  • Year: 2001
  • Department: Department of Physics
  • Annotation:
    Článek popisuje použití metod kvality zvuku pro hodnocení interieru vozidla

Sound Quality Research on Interior Sound of Cars

  • Authors: Kynčl, L., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Poster 2001. Praha: České vysoké učení technické v Praze, Fakulta elektrotechnická, 2001. pp. NS26.
  • Year: 2001

System of active attenution of higher modes in ducts

  • Department: Department of Physics
  • Annotation:
    The paper discussed possibilities of four-channel ANC sytem in a duct

Two-channel ANC in Experimental Duct

  • Department: Department of Physics
  • Annotation:
    Članek popisuje praktickou realizaci dvoukanálového ANc v potrubí

Active Control Applied to Fan Noise in a Duct

Active control of higher modes in a duct

  • Authors: prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Sborník 60. akustického semináře & 36. akustické konference. Praha: České vysoké učení technické v Praze, 2000. pp. 34-41. ISBN 80-01-02179-3.
  • Year: 2000

Active noise control in a duct with higher modes

Comparison of Acoustic Feedback Compensation Methods

  • Department: Department of Physics
  • Annotation:
    Článek srovnává čtyři metody kompenzace akustické zpětné vazby.

Experiences with local noise control

  • Department: Department of Physics
  • Annotation:
    Local active noise control in the presence on artifical head

Single Channel ANC Using X-LMS in Frequency Domain

  • Department: Department of Physics
  • Annotation:
    Članek popisuje aplikaci x-lms ve frekvenční oblasti v potrubí

Sound Quality Assessment of Vacuum Cleaner

  • Authors: prof. Ing. Ondřej Jiříček, CSc., Kynčl, L.
  • Publication: Proceedings of Workshop 2000. Praha: České vysoké učení technické v Praze, 2000. pp. 72. ISBN 80-01-02229-3.
  • Year: 2000
  • Department: Department of Physics
  • Annotation:
    Članek popisuje metody hodnocení kvality zvuku vysavačů

Sound quality evaluation in cars

  • Department: Department of Physics
  • Annotation:
    Paper sumarizes basic approach to sound quality assessment in cars

Study of the u-LMS Based ANC System

The use of active methods in cars

  • Department: Department of Physics
  • Annotation:
    The paper sumarize possible methods in interior and exterior noise control in cars.

Adaptive Feed Forward Control with Active Identification

  • Department: Department of Physics
  • Annotation:
    Adaptivní řízení v systému feed-forward s aktivní identifikací

Adaptive feed-forward control of broadband noise

Application of methods of acoustic feedback compensation

  • Department: Department of Physics
  • Annotation:
    Článek srovnává metody kompenzace akustické zpětné vazby

Experiences with Attenuation of Low-frequency Noise in Duct

Fan Noise Attenuation using Feed Forward Control

  • Department: Department of Physics
  • Annotation:
    Snizovani hluku ventilatoru v pomoci systemu feed-forward

Feedback compensation by Swinbanks' source in ANC system

Practical approach to ANC of fan noise with feedback compensation

Realization of one-channel ANC using X-LMS in frequency domain

  • Department: Department of Physics
  • Annotation:
    The paper demonstrates the possibility of usage X-LMS in transform domain for ANC.

A Gradient Impulse Method of Measuring Sound Absorption

  • Department: Department of Physics
  • Annotation:
    Gradientní impulsní metoda měření zvukové pohltivosti

Active Attenuation of Fan Noise in an Air-conditioning Duct

Active Noise Control in a Duct by Adaptive Feed-forward Control

Active Reduction of Radiated Sound Power

  • Department: Department of Physics
  • Annotation:
    Aktivní snižování výkonu vyzařovaného zdrojem zvuku

Application of x-LMS Algorithm for Fan Noise Reduction

  • Department: Department of Physics
  • Annotation:
    Použití algoritmu x-LMS pro snižování hluku ventilátoru

Fan Noise Attenuation by Single Channel LMS System

  • Department: Department of Physics
  • Annotation:
    Snižování hluku ventilátorů s užitím jednokanálové soustavy LMS

Noise and vibration, measurement and evaluation

  • Authors: Smatana, C., Hellmuth, T., Jandák, Z., prof. Ing. Ondřej Jiříček, CSc., Kozák, J., Krahulec, J., Liberko, M., Meller, M., Millerová, J., Schwarz, J., Šulc, J., Votýpka, B.
  • Publication: Praha: Sdělovací technika, 1998. ISBN 80-901936-2-5.
  • Year: 1998
  • Department: Department of Physics
  • Annotation:
    Book describes basic principles of perception and propagation of noise, its measurements and evaluation with respect to CR and EU standards. Measurements and evaluation of vibrations are included as well.

Noise control strategies in a duct

  • Department: Department of Physics
  • Annotation:
    Rewiew of two basic control strategies used in active noise control

Practical realization of single-channel ANC with compensation of acoustic feedback

  • Department: Department of Physics
  • Annotation:
    The paper deal with single channel feed-forward ANC system in a duct with feedback compensation.

Using the Acoustic Holography for Mapping of Sound Field of Real Sources

  • Department: Department of Physics
  • Annotation:
    Použití akustické holografie při měření reálných zdrojů

Acoustic Effects in Unipolar DC Corona

  • Authors: Aubrecht, L., Staněk, Z., Koller, J., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: Proceedings of 18th Symposium on Plasma Physics and Technology. Praha: ČVUT FEL, Katedra fyziky, 1997. pp. 232-233. ISBN 80-01-01641-2.
  • Year: 1997

Active Control of Sound in Wave-Guide

An Experimental Study of Active Control in a Duct

Basic Study of ANC in an Acoustic Wave-Guide

Experiences with Active Noise Control in Ducts

Implementation of In-duct Active Control

Narrow Band Implementation of ANC in Duct

The Application of a Gradient Analysis to Investigation of the Sound Absorption of Spatial Structures by Impulse Technique

  • Authors: Kyncl, Z., prof. Ing. Ondřej Jiříček, CSc., Červenka, M.
  • Publication: 34. akustická konference / 55. akustický seminář. Praha: Česká akustická společnost, 1997. pp. 85-90. ISBN 80-01-01690-0.
  • Year: 1997

Measurement of Nonlinear Waves in Hard-Walled Ducts

Noise of Automobile Alternator

  • Department: Department of Physics
  • Annotation:
    Clanek se zabyva merenim a potlacovanim elektromagnetickeho hluku alternatoru.

Noise of wind-turbines

  • Department: Department of Physics
  • Annotation:
    The paper deals with generation and noise of wind-turbines.

Principles of Active Control in Ducts

Study of the Diffraction Effect on the Circular and Rectangular Plates

  • Department: Department of Physics
  • Annotation:
    Clánek se zabývá numerickým modelováním a experimentálním ověřováním difrakčních jevů.

Transient Sound Energy Transfer I: Theory

  • Authors: Kyncl, Z., prof. Ing. Ondřej Jiříček, CSc.,
  • Publication: 33rd Conference on Acoustics - Building and Room Acoustics. Praha: Česká akustická společnost, 1996. pp. 108-111. ISBN 80-01-01536-X.
  • Year: 1996
  • Department: Department of Physics
  • Annotation:
    Časový průběh šíření transientní akustické energie je vyjádřen pomocí Eulerovy rovnice. K spektrálnímu vyjádření je použito Rayleighova-Parsevalova teorému.

Transient Sound Energy Transfer II: Experiments and Processing

  • Authors: prof. Ing. Ondřej Jiříček, CSc., Kyncl, Z., Červenka, M.
  • Publication: 33rd Conference on Acoustics - Building and Room Acoustics. Praha: Česká akustická společnost, 1996. pp. 100-103. ISBN 80-01-01536-X.
  • Year: 1996
  • Department: Department of Physics
  • Annotation:
    Clánek se zabývá měřením v transientním zvukovém poli.

Wind-turbines and measurement of noise

  • Department: Department of Physics
  • Annotation:
    The paper deals with baffle-plate method of wind-turbine noise measurement.

Aerodynamic Noise in Ducts. Preliminary Study for the ANC

Baffle Plate Method for Measurement of Noise Produced by Wind Turbines

Calibration of Sound Intensity Instruments in a One-Dimensional Sound Field

Measurement of Wind Turbine Noise by Microphone Bafflet in a Hard Plate

Diffracion of the Sound Impulse Wave by the Circular Aperture

  • Authors: Kyncl, Z., prof. Ing. Ondřej Jiříček, CSc., Kašpar, L., Zadražil, O.
  • Publication: Proceedings 31th Acoust. Conf. Praha: České vysoké učení technické v Praze, 1994. pp. 107-110. ISBN 80-01-01146-1.
  • Year: 1994

Gradient Analysis of Transient Sound Fields

  • Authors: prof. Ing. Ondřej Jiříček, CSc., Kyncl, Z., Kašpar, L.
  • Publication: Proceedings 31th Acoust. Conf. Praha: České vysoké učení technické v Praze, 1994. pp. 111-114. ISBN 80-01-01146-1.
  • Year: 1994

Responsible person Ing. Mgr. Radovan Suk