Loudness compensation, or simply loudness, is a setting found on some

hi-fi High fidelity (hi-fi or, rarely, HiFi) is the high-quality reproduction of sound. It is popular with audiophiles and home audio enthusiasts. Ideally, high-fidelity equipment has inaudible noise and distortion, and a flat (neutral, uncolored) ...

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. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

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

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. 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