The MPO is the loudest level of amplified sound to enter the ear canal, regardless of the loudness of the sound entering the hearing aid. It clipped the peaks of sound that exceeded the maximum power output, but resulted in distortion of the desired signal. The level at which compression begins is set by the hearing aid dispenser. Compression is used, also, to enable maximum amplification of soft sounds, less amplification of loud sounds, and none for very loud sounds. It improves sound quality, comfort, and listening.
Compression is available in analog and digital hearing aids.
Most hearing aid users benefit from compression. When a hearing aid uses wide dynamic range compression, it automatically controls volume. This means that theoretically a volume control dial is not necessary. But since some people prefer to control volume manually, many hearing aids have a volume control. Analog versus Digital Technology Analog hearing aids use electronic circuitry, and digital aids use computer mcrochips.