Reverberation time measurement method comparison: Interrupted source versus reference sound source

Many field measurements of sound isolation (e.g., impact noise reduction, airborne noise reduction, facade noise reduction) require adjustment of the measurement data to account for unfurnished rooms or to normalize the measurement results to a given reverberation time (e.g., 0.5 s). This adjustment or normalization is accomplished by measuring the amount of sound absorption/reverberation time in the room (typically, just in the receive room). The “interrupted noise source” method is commonly utilized, whereas a loudspeaker is used to generate high levels of pink noise, the signal is cut, and the resultant decay is measured to calculate the reverberation time. Recently, a newly published standard for facade noise reduction (SAE ARP6973A) recommends utilizing a reference sound source (which emits a calibrated broadband noise) to calculate the amount of absorption in a room and the reverberation time. This paper discusses the benefits/disadvantages of each method and presents field measurement results comparing the results of the two methods: interrupted source and reference sound source to determine whether the results obtained are comparable.