VU (VU meter)

A VU (Volume Unit) meter is an instrument that displays average audio levels, originally developed for broadcast. The VU meter has a relatively slow response (about 300 ms), so it shows average or perceptual loudness rather than very short transient peaks. In multicam audio/video productions it is commonly used to match input gains across cameras, wireless lavaliers and mixers, but it should be used alongside a peak meter to avoid digital clipping.

On a multicam interview shoot the audio engineer will set the camera inputs so the VU rests around 0 VU during a level sweep or test speech. Because the VU shows average loudness, this helps ensure the different recording channels produce similar perceived levels; a peak meter or the recorder's digital meters should be used in addition to catch short transients and prevent clipping. During rehearsal the engineer might also run a 1 kHz reference tone to verify consistent calibration between devices.