noun
infrasound; low-frequency sound
Technical term for sound waves below the typical human hearing range (generally under 20 Hz).
超低周波音は人間の耳には聞こえない。
Infrasound is inaudible to the human ear.
地震の前に超低周波音が観測されることがある。
Infrasound is sometimes detected before earthquakes.
Compound of 超 (super, ultra), 低周波 (low frequency), and 音 (sound).