Which term describes sound with frequencies below human hearing?

Which term describes sound with frequencies below human hearing?

• A. Audible sound
• B. Infrasound
• C. Ultrasound
• D. Subsonic

Answer: (B)

Frequencies below human hearing are called infrasonic (infrasound). Humans typically hear from about 20 Hz up to 20 kHz, so anything below roughly 20 Hz is inaudible and falls into this category. The term infrasonic precisely describes these very low frequencies. In contrast, audible sound lies within the normal hearing range, ultrasound refers to those frequencies above what we can hear (often used in medical imaging), and subsonic is generally a term from aerodynamics describing speeds below the speed of sound, not a frequency descriptor.

Frequencies below human hearing are called infrasonic (infrasound). Humans typically hear from about 20 Hz up to 20 kHz, so anything below roughly 20 Hz is inaudible and falls into this category. The term infrasonic precisely describes these very low frequencies. In contrast, audible sound lies within the normal hearing range, ultrasound refers to those frequencies above what we can hear (often used in medical imaging), and subsonic is generally a term from aerodynamics describing speeds below the speed of sound, not a frequency descriptor.