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PLoS One. 2014 Apr 30;9(4):e95464. doi: 10.1371/journal.pone.0095464. eCollection 2014.

Frequencies of inaudible high-frequency sounds differentially affect brain activity: positive and negative hypersonic effects.

Author information

1
Department of Liberal Arts, The Open University of Japan, Chiba, Japan.
2
Department of Early Childhood Education, Tokyo Seitoku College, Tokyo, Japan.
3
Department of Research and Development, Foundation for Advancement of International Science, Tsukuba, Japan; Research Council, Waseda University, Tokyo, Japan.
4
Department of Functional Brain Research, National Center of Neurology and Psychiatry, Kodaira, Japan.
5
Department of Liberal Arts, The Open University of Japan, Chiba, Japan; Department of Cyber Society and Culture, School of Cultural and Social Studies, The Graduate University for Advanced Studies (SOKENDAI), Kanagawa, Japan.
6
Department of Research and Development, Foundation for Advancement of International Science, Tsukuba, Japan.

Abstract

The hypersonic effect is a phenomenon in which sounds containing significant quantities of non-stationary high-frequency components (HFCs) above the human audible range (max. 20 kHz) activate the midbrain and diencephalon and evoke various physiological, psychological and behavioral responses. Yet important issues remain unverified, especially the relationship existing between the frequency of HFCs and the emergence of the hypersonic effect. In this study, to investigate the relationship between the hypersonic effect and HFC frequencies, we divided an HFC (above 16 kHz) of recorded gamelan music into 12 band components and applied them to subjects along with an audible component (below 16 kHz) to observe changes in the alpha2 frequency component (10-13 Hz) of spontaneous EEGs measured from centro-parieto-occipital regions (Alpha-2 EEG), which we previously reported as an index of the hypersonic effect. Our results showed reciprocal directional changes in Alpha-2 EEGs depending on the frequency of the HFCs presented with audible low-frequency component (LFC). When an HFC above approximately 32 kHz was applied, Alpha-2 EEG increased significantly compared to when only audible sound was applied (positive hypersonic effect), while, when an HFC below approximately 32 kHz was applied, the Alpha-2 EEG decreased (negative hypersonic effect). These findings suggest that the emergence of the hypersonic effect depends on the frequencies of inaudible HFC.

PMID:
24788141
PMCID:
PMC4005747
DOI:
10.1371/journal.pone.0095464
[Indexed for MEDLINE]
Free PMC Article

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