Comparison of the Steady State and Dynamic Characteristics of Sound Insulation With the Intelligibility of Transmitted Speech

The question of the intelligibility of speech in buildings is treated differently depending on whether the speech is spoken and heard within the same room.e.g. an auditorium, or has been transmitted from one room to another.In auditoria, it is considered to be a problem in the time domain with the emphasis on the rate of sound decay expressed in overall terms by the reverberation time and more precisely by the proportion of the energy that is received within the integration time of the ear.In contrast, the intelligibility of speech when transmitted between rooms is treated as a Ereguency domain problem and is taken to be due to the difference in mean sound pressure levels in source and receiving rooms expressed as a function of frequency, However, if we compare the sound decay patterns found in some sound transmission situations with those of auditoria whose reverberation times are generally considered to be much too long for good speech intelligibility (Figure l) , it is apparent that there can be as much if not more 'late' energy in the former case as in the latter.The aim of the work described in this paper was to assess how significant this phenomenon could be and, in particularly, whether walls and partitions with the same steady state sound insulation but with different dynamic characteristics could produce different levels of speech privacy.