Small Reverberation Chamber for Measuring the Sound Absorption of Materials at High Frequencies

Abstract

Construction of a model reverberation chamber, patterned after the Riverbank reverberation chamber on a scale of ten to one, allows measurement of the sound absorption coefficient of materials over the frequency range from 4 kc to over 30 kc. Knowledge of the absorption coefficients of materials at high frequencies is important in acoustic model studies of large silencing structures and of auditoriums. The model is also intended for study of the effect of changes in room configuration which might be considered for the full size reverberation chamber. Sound sources used in the model include a WE 633 dynamic microphone and an electrostatic tweeter. Instrumentation, measurement techniques, and limitations of reverberation time measurements at high frequencies are discussed. The absorption coefficients of a few materials useful in model work are presented.

Method for Establishing a Traveling Wave Sound Field with Adaptive Control in a Water-Filled Sound Tube

“…The basic principle of the acoustic tube measurement is to generate plane waves below the first-order cut-off frequency in the acoustic tube by controlling the sound source at one end of the acoustic tube [12]. The acoustic tube method, also known as the impedance tube method, can be divided into standing wave tube method [13][14][15][16][17][18], pulse tube method [19][20][21][22][23], and traveling wave tube (TWT) method from the perspective of the sound field formed in the tube.…”