Evaluating standard airborne sound insulation measures in terms of annoyance, loudness, and audibility ratings

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Abstract
This paper reports the results of an evaluation of the merits of standard airborne sound insulation measures with respect to subjective ratings of the annoyance and loudness of transmitted sounds. Subjects listened to speech and music sounds modified to represent transmission through 20 different walls with sound transmission class (STC) ratings from 34 to 58. A number of variations in the standard measures were also considered. These included variations in the 8-dB rule for the maximum allowed deficiency in the STC measure as well as variations in the standard 32-dB total allowed deficiency. Several spectrum adaptation terms were considered in combination with weighted sound reduction index (Rw) values as well as modifications to the range of included frequencies in the standard rating contour. A STC measure without an 8-dB rule and an Rw rating with a new spectrum adaptation term were better predictors of annoyance and loudness ratings of speech sounds. Rw ratings with one of two modified Ctr spectrum adaptation terms were better predictors of annoyance and loudness ratings of transmitted music sounds. Although some measures were much better predictors of responses to one type of sound than were the standard STC and Rw values, no measure was remarkably improved for predicting annoyance and loudness ratings of both music and speech sounds.

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