Application of loudness level to temporally varying sounds



Most of the environmental noises are temporally varying and include various frequency components.  Various methods for evaluating the environmental noises have been proposed.  Among them, the method for calculating loudness level was first standardized in 1975 as ISO 532, including Stevens’ and Zwicker’s methods.  Unfortunately, these methods can only be applied to steady state sounds.  On the other hand, Aeq (Equivalent Continuous A-weight Sound Pressure Level) is standardized for the evaluation of level fluctuating environmental sounds as ISO 1996.  In , the energy mean and A-weighting are used for averaging temporal fluctuation and frequency weighting, respectively.  The present authors with their colleagues have conducted many psychological experiments using artificial sounds and actual sounds since 1970’s and have being introduced that p (Loudness-based Method), which is a combination of ISO 532 for frequency weighting and ISO 1996 for temporal level fluctuation, is a good method for evaluating various kinds of environmental sounds. ISO 532-1 (Zwicker’s method) has been revised including the temporal fluctuation into consideration in 2017, in which p has been adopted as a note.  The merit of p will be introduced in this paper presenting many examples.