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 ...

Volume unit (VU) meters are cool — it’s an undeniable fact. For some reason, humans just dig lights that flash along with sounds. You can build a VU meter using LEDs, or bulbs if you’re trapped in ...