Loudness compensation, or simply loudness, is a setting found on some hi-fi equipment that increases the level of the high and low

frequencies Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is e ...

. This is intended to be used while listening at low-volume levels, to compensate for the fact that as the

loudness In acoustics, loudness is the subjective perception of sound pressure. More formally, it is defined as, "That attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of ph ...

of audio decreases, the ear's lower sensitivity to extreme high and low frequencies may cause these signals to fall below the

threshold of hearing The absolute threshold of hearing (ATH) is the minimum sound level of a pure tone that an average human ear with normal hearing can hear with no other sound present. The absolute threshold relates to the sound that can just be heard by the organis ...

. As a result audio material may become thin sounding at low volumes, losing bass and treble. The loudness compensation feature applies equalization and is intended to rectify this situation.

Calibration

Correct loudness compensation requires a calibrated system with known listening level. Audio level at a listener's ears depends on the listening environment, listener position, speaker sensitivity as well as amplifier gain. For loudness compensation to work correctly the playback system must also accurately assume what volume level was used in mastering. For movie soundtracks this reference volume level is an industry standardSMPTE 202m-1998 and can be used by manufacturers to provide a loudness feature that works with a reasonable degree of accuracy. A home theater product that provides a reference level indication on the volume control can be expected to work well with movie soundtracks.

References

Tone, EQ and filter {{Sound-tech-stub