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The hypersonic effect is a term coined to describe a phenomenon reported in a controversial scientific study by Tsutomu Oohashi et al.,〔T. Oohashi, E. Nishina, M. Honda, Y. Yonekura, Y. Fuwamoto, N. Kawai, T. Maekawa, S. Nakamura, H. Fukuyama, and H. Shibasaki. (Inaudible high-frequency sounds affect brain activity: Hypersonic effect. ) Journal of Neurophysiology, 83(6):3548–3558, 2000.〕 which supports the idea that although humans cannot consciously hear ultrasound (sounds at frequencies above approximately 20 kHz),〔http://scitation.aip.org/content/asa/journal/jasa/122/3/10.1121/1.2761883〕〔http://www.aes.org/e-lib/browse.cfm?elib=10005〕〔http://www.aes.org/e-lib/browse.cfm?elib=13185〕〔http://www.aes.org/e-lib/browse.cfm?elib=12375〕 the presence or absence of those frequencies has a measurable effect on their physiological and psychological reactions. Attempts to independently reproduce these results have so far been unsuccessful.〔〔 Numerous other studies have contradicted the portion of the results relating to the subjective reaction to high-frequency audio, finding that people who have "good ears"〔Lehrman, Paul D. ("The Emperor's New Sampling Rate." ) ''Mix'', April 1, 2008. Retrieved on October 13, 2009.〕 listening to Super Audio CDs and high resolution DVD-Audio recordings〔Meyer, E. Brad; David R. Moran. September 2007. (''Audibility of a CD-Standard A/DA/A Loop Inserted into High-Resolution Audio Playback: Sources, Venues, and Equipment''. ) Boston Audio Society. Retrieved on October 14, 2009.〕 on high fidelity systems capable of reproducing sounds up to 30 kHz〔SLS Loudspeakers. (S1266 ). Retrieved on October 14, 2009.〕 cannot tell the difference between high resolution audio and the normal CD sampling rate of 44.1 kHz.〔〔Meyer, E. Brad; David R. Moran. September 2007. (''Audibility of a CD-Standard A/DA/A Loop Inserted into High-Resolution Audio Playback''. ) AES E-Library. Retrieved on October 13, 2009.〕 ==Favoring evidence== In research published in 2000 in the Journal of Neurophysiology,〔 researchers described a series of objective and subjective experiments in which subjects were played music, sometimes containing high-frequency components (HFCs) above 25 kHz and sometimes not. The subjects could not consciously tell the difference, but when played music with the HFCs they showed differences measured in two ways: * EEG monitoring of their brain activity showed statistically significant enhancement in alpha-wave activity * The subjects preferred the music with the HFCs No effect was detected on listeners in the study when only the ultrasonic (frequencies higher than 24 kHz) portion of the test material was played for test subjects; the demonstrated effect was only present when comparing full-bandwidth to bandwidth-limited material. It is a common understanding in psychoacoustics that the ear cannot respond to sounds at such high frequency via an air-conduction pathway, so one question that this research raised was: does the hypersonic effect occur via the "ordinary" route of sound travelling through the air passage in the ear, or in some other way? A peer-reviewed study in 2006 seemed to confirm the second of these options, by testing the different effect of HFCs when presented via loudspeakers or via headphones - the hypersonic effect did not occur when the HFCs were presented via headphones.〔T. Oohashi, N. Kawai, E. Nishina, M. Honda, R. Yagi, S. Nakamura, M. Morimoto, T. Maekawa, Y. Yonekura, and H. Shibasaki. (The role of biological system other than auditory air-conduction in the emergence of the hypersonic effect. ) Brain Research, 1073:339–347, February 2006.〕 The 2006 study also investigated the ''comfortable listening level'' (CLL) of music with and without HFCs, an alternative way of measuring subject response to the sound. The CLL for the music with HFCs was higher than that for the music without HFCs - this provides a quantitative way to demonstrate general listener preference for the music with HFCs.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hypersonic effect」の詳細全文を読む スポンサード リンク
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