A Very Large VU Meter Indeed
It used to be a must-have on any hi-fi, a pair of moving coil meters or LED bar graphs, the VU meter. Your 1980s boombox would have had them, for example. VU, for “Volume Units”, is a measure of audio level, and the fashion for its visual measure in consumer audio equipment seems now to have largely passed.
https://hackaday.com/2017/05/16/a-very-large-vu-meter-indeed/