Hearing_impairment A hearing impairment or deafness is a full or partial decrease in the ability to detect or understand sounds. Deaf culture, they prefer the terms Deaf and Hard of Hearing.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.