Investigations on Cerebral Hemisphere Activities Related to Subjective Preference of the Sound Field, Published for 1983 - 2003
Theory of subjective preference of the sound field in a concert hall is described for a number of subjects, based on the model of human auditory-brain system. The model consists of the autocorrelation function (ACF) mechanism and the interaural crosscorrelation function (IACF) mechanism for signals arriving at two ear entrances, and the specialization of human cerebral hemispheres [Ando, Concert Hall Acoustics, Springer-Verlag, Heidelberg, 1985; Architectural Acoustics, AIP/Springer-Verlag, New York, 1998]. It is considered that subjective preference is the most primitive response of living creatures, and the direction of preference may be maintaining life. It is assumed that information corresponding to subjective preference of sound fields can be found in brain activities, such as in auditory-brainstem response (ABR), slow vertex responses (SVR), electroencephalography (EEG) and magnetoencephalography (MEG). In fact, this has been discovered in the effective duration, te, ACF of the alpha waves in EEG and MEG related to subjective preference. The temporal factors of sound fields such as initial time delay gap between the direct sound and the first reflection (Dt1). and subsequent-reverberation time (Tsub) are deeply associated with the left hemisphere. And the spatial factors such as magnitude of interaural cross-correlation (IACC) and listening level (LL) are associated with the right. Surprisingly, individual differences in subjective preference appears in the difference of ACF effective duration (te) of the alpha wave in EEG and MEG. Large individual differences of subjective preference are observed mainly in temporal factor Dt1 and Tsub and LL, but not in the typical spatial factor IACC. Individual differences in LL may be related to individual hearing levels. These evidences support the theory of subjective preference described based on the model of human auditory-brain system. This theory may be applied for individual level of subjective preference as well.
Key words: subjective preference, autocorrelation functions of the alpha waves, auditory-brainstem response (ABR), slow vertex responses (SVR), electroencephalography (EEG), magnetoencephalography (MEG), model of auditory-brain system, specialization of cerebral hemispheres