Related Experiment Videos
Inaudible high-frequency sounds affect brain activity: hypersonic effect.
T Oohashi1, E Nishina, M Honda
1Department of KANSEI Brain Science, ATR Human Information Processing Research Laboratories, Kyoto 619-0288, Japan.
Journal of Neurophysiology
|June 10, 2000
Summary
High-frequency components (HFCs) above human hearing significantly impact brain activity and sound perception. This study reveals a new "hypersonic effect" where inaudible sound frequencies influence neural responses and listener enjoyment.
Area of Science:
- Auditory Neuroscience
- Psychoacoustics
- Neurophysiology
Background:
- Human hearing is typically limited to frequencies below 20 kHz.
- The influence of inaudible high-frequency components (HFCs) on acoustic perception is not well understood.
- Gamelan music provides a natural sound source rich in HFCs.
Purpose of the Study:
- To investigate whether inaudible HFCs affect brain activity and acoustic perception.
- To explore the neural mechanisms underlying responses to complex sounds with HFCs.
- To identify and characterize a potential new auditory phenomenon.
Main Methods:
- Noninvasive physiological measurements including electroencephalography (EEG) and positron emission tomography (PET).
- Subjects were exposed to gamelan music components: low-frequency (LFC) and high-frequency (HFC) above 22 kHz.
- Analysis of brain electrical activity (alpha-EEG) and regional cerebral blood flow (rCBF).
Main Results:
- HFCs alone were not perceived as sound.
- Combined LFC and HFC exposure significantly increased occipital alpha-EEG power compared to LFC alone.
- rCBF increased in the brain stem and left thalamus when HFCs were present with LFCs.
- Alpha-EEG power correlated with rCBF in the left thalamus.
- Sounds with HFCs were perceived as more pleasant.
Conclusions:
- Inaudible HFCs can significantly modulate brain activity and auditory perception.
- A novel auditory response, termed the "hypersonic effect," is suggested.
- This effect involves neural processing in the brain stem and thalamus, influencing subjective pleasantness.