Deafness

A hearing impairment or hearing loss is a full or partial decrease in the ability to detect or understand sounds.
Caused by a wide range of biological and environmental factors, loss of hearing can happen to any organism that perceives sound.
Sound waves vary in amplitude and in frequency. Amplitude is the sound wave's peak pressure variation. Frequency is the number of cycles per second of a sinusoidal component of a sound wave. Loss of the ability to detect some frequencies, or to detect low-amplitude sounds, that an organism naturally detects, is a hearing impairment.