Abstract
The Rayleigh Integral Method, the Integral Transform Method and the Discrete Calculation Method are all vibration velocity-based measurement methods to determine the radiated sound power from planar objects. Even though all these three methods are based on a well-established theoretical background, which has been known for long time, they are only now gaining popularity in the building acoustics field and the building acoustics community is still rather new to them. They offer advantages compared to the standard methods specially in the low frequency range or on special applications with articulated boundary conditions. In this paper, we want to summarize the three methods in one place to highlight their different theoretical foundations. We present a numerical benchmark of these three methods, based on a simple panel with varying boundary conditions, highlighting similarities and differences between them. In a second step, we compare the radiated sound power levels obtained by the three methods with results obtained by a standard measurement procedure according to the ISO10140-3, under excitation by an ISO tapping machine. Finally, we present the application of the methods to determine the in-situ impact noise level of a floor structure: a complex system with challenging boundary conditions. The results show a good agreement between all the tested methods, as long as the respective requirements are satisfied. The results also demonstrate how the vibration velocity-based measurement methods can have a broader application compared to the standard laboratory method and deliver additional information on complex test objects.
Highlights
Building acoustic measurements are generally carried out according to appropriate standards
For the CCCC BCs, no difference is observed between the results obtained with the grid size 60 Â 50 and 30 Â 25 as expected, since both grid sizes fulfill the criteria over the whole frequency range of interest
The averaging between tapping machine excitation position goes in the same direction. Both aspects possibly reduce the discrepancies between the methods. These results demonstrate that all three methods Rayleigh Integral Method (RIM), ITM and Discrete Calculation Method (DCM) are valuable alternatives to the standard method to determine the radiated sound power of a planar object due to impact excitation
Summary
Building acoustic measurements are generally carried out according to appropriate standards. When looking at the impact sound insulation the relevant standards for laboratory measurements is the ISO 10140-3 [1]. The accuracy of the results in the low frequencies is limited because the sound field is not diffuse. This point is rather critical considering that frequencies below 50 Hz are of great importance when considering impact sound insulation and annoyance in lightweight buildings [2]. Because of this and the fact that scanning laser vibrometers and multichannel measure-
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