著者

西口 敏行 Toshiyuki Nishiguchi

出版者

電気通信大学

巻号頁・発行日

2009-03-24

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It is generally accepted that the frequency bandwidth of human hearing byair conduction does not far exceed 20 kHz. However, some papers discussedthe influence of extending the frequency by such high resolution audioformats on the auditory impression and brain activity. Studies on thebandwidth of human hearing are important for defining the frequencybandwidth for sound recordings and for developing electro-acoustictransducers, next-generation broadcasting systems and the definition of therecording format of audio archives.If differences of sound impression among high resolution audio formatsindeed exist, it is necessary to consider two factors: influence of reproductionof very high frequency, and difference of sound quality in auditory frequencyband among the sampling formats.Regarding the former factor, we conducted subjective evaluation testsconcerning the influence of very high frequency components on the humanperception in musical sounds. To make a precise evaluation, the test systemwas designed to exclude any influence from very high frequency componentsin the audible frequency range. Tests showed that the subjects coulddiscriminate between musical sounds with and without very high frequencycomponents.While, to study the difference of sound quality in the auditory frequencyband among several high sampling digital recording formats, we alsoconducted subjective evaluation tests of perceptual discrimination amongthe following digital recording formats: 24 bit/48 kHz, 24 bit/192 kHz andDSD. The results showed no significant difference, namely, sound quality ofthe auditory frequency band in this experiment system does not depend onthe sampling format.According to the results of these tests, extension of the frequency range byhigh resolution audio affects the perception of sound and it is caused by thereproduction of very high frequency components. It could be worth recordingmusic by high resolution audio systems with a very wide frequency range.However various issues have been pointed out regarding the very highfrequency band, i.e., the non-linear distortion of the amplifier orloudspeaker, time jitter and so on. Very accurate handling is required toreproduce the very high frequency components.