Construction and Verification of Small-Sized and Low Cut-Off Frequency Reverberant Chamber

Reverberant chambers are important in acoustical measurement due to their diffuseness in sound fields. However, design and construction of small reverberant chambers are challenging, since their cut-off frequencies are inversely proportional to their volume. This work is to design and construct a small-size reverberant chamber of not bigger than 3 m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> volume, having low cut-off frequency not higher than 400 Hz. The design started with simulation so that the chamber shape can be adjusted to be irregular and complied with ISO standard. After construction of the chamber, performance evaluations of the chambers with four types of corner diffuser installation, were performed based on ISO 354 and ISO 3741 standards. Diffuseness of sound field in the chamber was verified using standard deviation of measured SPLs. After evaluation, it was found that the constructed reverberant chamber with the type-4 corner diffuser installation met the requirements for having a diffuse sound field at 400 Hz cut-off frequency. The chamber also has low background noise. The noise levels in frequency octave of 200 – 5000 Hz band were between 4-16 dB.