The role of biological system other than auditory air-conduction in the emergence of the hypersonic effect

Abstract

Although human beings cannot perceive elastic vibrations in the frequency range above 20 kHz, nonstationary sounds containing a wealth of inaudible high-frequency components (HFC) above the human audible range activate deep-lying brain structures, including the brainstem and thalamus and evoke various physiological, psychological, and behavioral responses. In the previous reports, we have called these phenomena collectively "the hypersonic effect." It remains unclear, however, if vibratory stimuli above the audible range are transduced and perceived solely via the conventional air-conducting auditory system or if other mechanisms also contribute to mediate transduction and perception. In the present study, we have examined the emergence of the hypersonic effect when inaudible HFC and audible low-frequency components (LFC) were presented selectively to the ears, the entrance of an air-conducting auditory system, or to the body surface including the head which might contain some unknown vibratory sensing mechanisms. We used two independent measurements based on differing principles; one physiological (alpha 2 frequency of spontaneous electroencephalogram [alpha-EEG]) and the other behavioral (the comfortable listening level [CLL]). Only when the listener's entire body surface was exposed to HFC, but not when HFC was presented exclusively to the air-conducting auditory system, did both the alpha-EEG and the CLL significantly increase compared to the presentation of LFC alone, that is to say, there was an evident emergence of the hypersonic effect. The present findings suggest that the conventional air-conducting auditory system alone does not bring about the hypersonic effect. We may need to consider the possible involvement of a biological system distinct from the conventional air-conducting auditory nervous system in sensing and transducing high-frequency elastic vibration above the human audible range.

Physical and Chemical Factors that Improve Epidermal Permeability Barrier Homeostasis

“…However, Oohashi and his coworkers demonstrated that ultrasound at a frequency above 20000 Hz (20 kHz) influences human brain electrical activity and systemic hormonal levels (Oohashi 2000) (Oohashi 2006) (Kawai 2001) (Yagi 2003). Interestingly, these effects did not involve the ear (Oohashi 2006).…”

High-resolution music with inaudible high-frequency components produces a lagged effect on human electroencephalographic activities

“…A PET study showed that brainstem and thalamus areas were more activated when hearing full-range sounds as compared with high-cut sounds [4]. Moreover, full-range sounds were perceived to be comfortable at a higher level of sound intensity than high-cut sounds [5][6][7]. Some studies have shown that full-range sounds produce better subjective ratings of sound quality (e.g.…”

“…at the later part of a 180-, 200-, or 400-s listening epoch) [4][5][6]. This phenomenon is atypical in the field of auditory perception research, because a standard test for sound quality usually compares sound samples with a shorter duration (e.g.…”

Sensory Systems of Epidermal Keratinocytes

“…However, Oohashi and his coworkers demonstrated that ultrasound at a frequency above 20,000 Hz (20 kHz) infl uences human brain electrical activity and systemic hormonal levels [ 69,87,88,122 ] . Interestingly, these effects did not occur via the ears [ 88 ] . On the other hand, a recent study demonstrated that a slight, inaudible air puff on the skin infl uenced auditory perception [ 50 ] .…”

“…Oohashi and his coworkers demonstrated that inaudible sound was sensed at the body surface, excluding the ears, and infl uenced brain electrical activity [ 88 ] , but the mechanism involved is still unknown. Feldmann has suggested that a structure in human eccrine gland has the ability to detect very high frequency (gigahertz) sound [ 46 ] .…”