Chapter 8 - Subjective evaluation for coherent region in reverberant space

Abstract

The subjective impression of acoustic space depends largely on the distance from a sound source rather than solely a room's acoustic parameters such as the reverberation time of the space. This chapter develops the sound field close to the sound source in a reverberant space. The sound field is the coherent region in which a sound wave travels as a spherical wave from a point source, even in reverberant space. The subjective impression on the sound source distance in the field is intriguing from an audio-engineering perspective such as sound recording. Experimental data imply that the sound source distance can be perceptually determined even in the coherent region under diotic listening conditions. Magnitude frequency responses vary as a function of the sound source distance, and the subjective judgments on the distance are well correlated with the magnitude frequency responses. The loudness of musical sounds or the intelligibility of speech utterances can also be subjectively determined in the coherent region. The subjective evaluation is greatest at around the midpoint of the coherent region. Enhancement or deterioration due to the sound source distance might be interpreted as the spectral similarity or dissimilarity of narrowband temporal envelopes.