Abhishek Singh, M. Tech.

The article presents preliminary study of sound power measurement using sound intensity and laser Doppler vibrometry.

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.

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.