増田 斐那子

A previous study found that spatial release from masking (SRM) could be observed under virtual reverberant environments using a first order Ambisonic-based sound reproduction system, however, poor localisation accuracy made it difficult to examine effect of varying reverberation time on SRM. The present study follows on using higher order Ambisonics (HOA) to examine how benefits from SRM vary in different spatial acoustics. Subjective speech intelligibility was measured where four room acoustics:reverberation time (RT)= 0.7 s (clarity (C50)= 15.9 dB, 6.8 dB) RT= 1.7 s (C50= 10.3 dB, 3.3 dB) were simulated via a third order Ambisonics system with a 16 channel spherical loudspeaker array. The masker was played from 8 azimuthal angles (0, ±45, ±90, ±135, 180 degrees) while the target speech was played from 0 degree. The listeners are deemed to benefit from SRM if their intelligibility scores were higher when the masker was projected from a different angle than that of the target. We found while listeners could benefit from SRM at C50 = 15.9 dB and 10.3 dB, the benefit starts to diminish at C50 = 6.8 dB, and listeners could no longer benefit from SRM at C50 = 3.3 dB.

Perceiving non-native sounds in adverse listening environments is challenging, even for proficient learners. An identification experiment in quiet, three reverberant (RT = 0.78 s, 1.12 s, 1.43 s) and multispeaker babble+reverberant environments was carried out to investigate the relation of listening environments and non-native language proficiency. This research aims to elucidate (1) Japanese and English listeners' identification of intervocalic English consonants in quiet and adverse listening environments, and (2) the correlation of identification rates with the Japanese listeners' TOEIC (R) scores, age of onset of English acquisition and length of residence in English-speaking countries. Results showed (1) English listeners achieved significantly higher overall identification rates compared to Japanese listeners on the subset of 11 consonants /f d(3) 3 l r s integral theta partial derivative v z/ that are often difficult for Japanese to accurately identify, and (2) positive correlations between identification rates and English proficiency measured by means of TOEIC (R) scores and LOR. Analysis of misperception patterns revealed that an increased amount of background disturbance led proficient listeners' misperception patterns to resemble those of the lower proficiency listeners, as in the example of native listeners misperceiving /g/ as /partial derivative/ in RT=1.12s and highly proficient Japanese misperceiving /g/ as /partial derivative/, /r/, and /l/, and lower group as /partial derivative/ and /l/. The degradation of identification accuracy as background disturbance increased shed light on how one's L1 and L2 proficiency influence speech perception. (c) 2016 Elsevier B.V. All rights reserved.