Ses lateralizasyonunda kulaklar arası zaman ve seviye ipuçlarının entegrasyonunun çeşitlilik kombinasyonu perspekti ne dayalı olarak modellenmesi

A sound source with non-zero azimuth leads to interaural time and level differences. Studies on the hearing system imply that these cues are encoded in different parts of the brain, but combined to produce a single lateralization percept. According to the duplex theory of sound lateralization, ITD and ILD play a more significant role, respectively, in low- and high-frequency stimulations. The current study investigates the relative weights of these two cues based on the error rate data obtained from two major two-alternative forced-choice experiments. In the experiments, ITD and ILD values were extracted from a generic head-related transfer function (HRTF). In experiment I, three different sounds containing either only low frequencies, or only high frequencies, or both were lateralized by imposing these ITD and ILD values. The subjects' lateralization error rate data indicate that the performance of the binaural hearing system based on ITD and ILD cues undergo a linear combination based on the maximum ratio combining approach. In experiment II, a complex sound consisting of two low- and seven high-frequency harmonic tones was used as test sound. Each stimulus consisted of a reference sound having the ITD-ILD pair of a certain azimuth and a probe sound that was different from the reference sound in either its ITD or in its ILD or in both. Subjects indicated the direction of the shift they perceived in the lateralization of sound. The error rate data showed that the weights of the two cues change with the azimuth of the sound source. Based on the SNR values obtained from the error rate data, it was shown that the two pieces of spatial information supplied by ITD and ILD are combined in the brain, but not additively for shifts in lateral positions around small azimuths. The integration model of the ILD and ITD cues was defined by a diversity combination approach incorporating the observed directional bias with inward preference