Scope:

ASTM E596-96 test method covers the measurement of noise reduction of sound isolating enclosures when placed in a reverberation room. This gives details about the sound-isolating enclosures and helps in ranking them with respect to noise isolation class. The results obtained from this method help in quality control, research, and performance evaluation of various sound-isolating enclosures. 

Procedure:

The sound-isolating enclosure is prepared and placed in a reverberation room. The noise levels are adjusted and measured with respect to one-third octave bands.  The one-third octave band sound pressure is measured on the onset of bands of random noise. The noise reduction data is taken and stands for the difference between the space-averaged sound pressure level in the reverberation room and that in the enclosure. The noise isolation data then helps in the determination of the noise isolation class.

Specimen Size:

Specimen size should be as per the requirements. In this case, a one-third octave filter set is used with its frequency varying from 125 to 4000 Hz. The signal level should be at least 10 dB above the background noise level.  

Data:

The signal level is corrected by applying the formula if the background noise level is between 5 and 10dB, where ‘L’ stands for the signal level, and ‘NR’ stands for the noise reduction.