![]() ![]() However, it remains unclear what kind of psychological and cognitive states are associated with this effect. Interestingly, this effect appears with a considerable delay (i.e., 100–200 s after the onset of music). In these studies, only the presence or absence of inaudible high-frequency components is manipulated while the sampling frequency and the bit depth are held constant. This effect is often called “hypersonic” effect. ![]() In contrast to this conventional digital recording process in which inaudible high-frequency components are cut off, high-resolution music that retains such components has been repeatedly shown to affect human electroencephalographic (EEG) activity ( Oohashi et al., 2000, 2006 Yagi et al., 2003a Fukushima et al., 2014 Kuribayashi et al., 2014 Ito et al., 2016). This reduction is based on the knowledge that sounds above 20 kHz do not influence sound quality ratings ( Muraoka et al., 1981) and do not appear to produce evoked brain magnetic field responses ( Fujioka et al., 2002). However, in conventional digital audio, sampling frequency is usually restrained so that sounds above 20 kHz are cut off in order to reduce file sizes for convenience. The higher sampling frequency enables higher frequency sound components to be reproduced, because one-half of the sampling frequency defines the upper limit of reproducible frequencies (as dictated by the Nyquist–Shannon sampling theorem). The present investigation used physiological, behavioral, and subjective measures to provide evidence that high-resolution audio affects human psychophysiological state without conscious awareness. What kind of advantage does the latest digital audio have for human beings? This question has not been sufficiently discussed. A higher sampling frequency makes the digitization of sound more accurate in the time-frequency domain, whereas a greater bit depth increases the resolution of the sound. Bit depth is the number of possible values in each sample and expressed as a power of two. Sampling frequency means the number of samples per second taken from a sound source through analog-to-digital conversion. Because of a higher sampling frequency and a greater bit depth than conventional low-resolution audio such as compact disks (CDs), it provides a closer replication of the real analog sound waves. High-resolution audio has recently emerged in the digital music market due to recent advances in information and communications technologies. 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. Only a subjective rating of inactive pleasantness after listening was higher for the excerpt with high-frequency components than for the other excerpt. The participants did not distinguish between these excerpts in terms of sound quality. 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. Reaction times and error rates did not change during the task and were not different between the excerpts. 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. Bach (on cembalo, 24-bit quantization, 192 kHz A/D sampling), with or without inaudible high-frequency components, while performing a visual vigilance task. The present study examined this possibility by having 22 participants listen to two types of a 400-s musical excerpt of French Suite No. However, no previous studies have explored whether sound sources with high-frequency components affect the arousal level of listeners. Traditionally, alpha-band EEG activity has been associated with arousal level. ![]() 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. Previous studies of high-resolution audio have mainly focused on the effect of such high-frequency components. ![]() The higher sampling frequency enables inaudible sound components (above 20 kHz) that are cut off in low-resolution audio to be reproduced. High-resolution audio has a higher sampling frequency and a greater bit depth than conventional low-resolution audio such as compact disks.
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