What is the term for waves with a lower frequency than the human ear can perceive?

Waves with a lower frequency than the human ear can perceive are referred to as infrasonic waves. Human hearing typically ranges from about 20 Hz to 20 kHz, and anything below 20 Hz is considered infrasonic. These low-frequency sound waves are often associated with natural events such as earthquakes or can be produced by machinery. Infrasonic waves are significant in various fields, including geology and environmental science, as they can provide information about phenomena occurring beyond human auditory perception.

Other terms like ultrasonic waves refer to frequencies above human hearing, and audible waves signify frequencies within the human hearing range, while subsonic is less commonly used and can describe speeds, particularly in aviation. Thus, infrasonic accurately captures the definition of those low-frequency waves that are beyond our auditory capability.