In sound reproduction, the meter, whether peak or not, is usually meant to correspond to the perceived loudness of a particular signal.
The term peak is used to denote the meter's ability, regardless of the type of visual display, to indicate the highest output level at any instant.
[1] In modern audio equipment, peak meters are usually made up of a series of LEDs (small lights) that are placed in a vertical or horizontal bar and lit up sequentially as the signal increases.
A meter can be implemented with a classic moving needle device such as those on older analog equipment (similar in appearance in some ways to a pressure gauge on a bicycle pump), or by other means.
The analog VU meters are actually closer to the human ear's perception of sound level because the response time was intentionally slow - around 300 milliseconds,[2] and thus, many audio engineers and sound professionals prefer to use older analog style metering[citation needed] because it more accurately relates to what a human listener will experience in terms of relative loudness.