Authors: Kuribayashi, R., & Nittono, H.
Title: High-resolution audio with inaudible high-frequency components induces a relaxed attentional state without conscious awareness (聞こえない高周波成分を含むハイレゾ音源を聞くと意識には上らないがリラックスした注意状態が生じる)
Journal(書誌情報）: Frontiers in Psychology, 8:93
Abstract: High-resolution audio has a higher sampling frequency and a greater bit depth than conventional low-resolution audio such as compact disks. The higher sampling frequency enables inaudible sound components (above 20 kHz) that are cut off in low-resolution audio to be reproduced. Previous studies of high-resolution audio have mainly focused on the effect of such high-frequency components. It is known that alpha-band power in a human electroencephalogram (EEG) is larger when the inaudible high-frequency components are present than when they are absent. Traditionally, alpha-band EEG activity has been associated with arousal level. However, no previous studies have explored whether sound sources with high-frequency components affect the arousal level of listeners. The present study examined this possibility by having 22 participants listen to two types of a 400-s musical excerpt of French Suite No. 5 by J. S. Bach (on cembalo, 24-bit quantization, 192 kHz A/D sampling), with or without inaudible high-frequency components, while performing a visual vigilance task. High-alpha (10.5-13 Hz) and low-beta (13-20 Hz) EEG powers were larger for the excerpt with high-frequency components than for the excerpt without them. Reaction times and error rates did not change during the task and were not different between the excerpts. The amplitude of the P3 component elicited by target stimuli in the vigilance task increased in the second half of the listening period for the excerpt with high-frequency components, whereas no such P3 amplitude change was observed for the other excerpt without them. The participants did not distinguish between these excerpts in terms of sound quality. Only a subjective rating of inactive pleasantness after listening was higher for the excerpt with high-frequency components than for the other excerpt. The present study shows that high-resolution audio that retains high-frequency components has an advantage over similar and indistinguishable digital sound sources in which such components are artificially cut off, suggesting that high-resolution audio with inaudible high-frequency components induces a relaxed attentional state without conscious awareness.
著者Contact先の email: nittono[at]hus.osaka-u.ac.jp (入戸野 宏)
日本語によるコメント: 耳には聞こえない高周波成分（> 20 kHz）を残したディジタル音源（ハイレゾ）と，それをカットした同じ音源は，意識的には区別できません。しかし，前者を聴取すると脳波のアルファ帯域パワーが増大します。その心理学的意義を調べるために，今回の実験では，2つの音源間で視覚ヴィジランス課題の成績を比較しました。その結果，高周波成分を残した音源を聴くと，アルファ帯域パワーが増えるが，行動成績は低下しないこと，事象関連電位のP3（P300）成分の振幅が聴取期間の後半で増加することが分かりました。これらの知見は，高周波帯域を残した音源は，眠気を誘うのではなく，注意状態を高める効果があることを示唆しています。