THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

12.8 Measuring Transmission Loss 293Figure 12.8. Setup for a transmission loss measurement.than that through the evaluation specimen. Sound level is measured in the sourcechamber and the receiving chamber with a microphone system, a measuring amplifier,and filter. The measured sound is filtered to mitigate the effect of backgroundnoise on the measurement procedures, with the filter settings being identical for thegenerated sound and the measuring sound filters. The sound level may be averagedby rotating the microphone about its base on the mounting tripod. The transmissionloss is found by applying the measured results in the following equation:( )AmTL = L S − L R + 10 logA RwhereL S = average sound level in the source chamberL R = average sound level in the receiving chamberA m = area of the material under investigationA R = equivalent absorption area of the receiving room.Another measurement setup is given in Figure 12.9. A pink noise generator,filters, audio power amplifier, and speaker constitute the sound source system.A computer-controlled analyzer incorporates a random noise generator and