Glossary definition of 'VU Meter'A meter designed originally to measure and standardise the levels in telephone lines. It is defined in ANSI C16.5-1942, British Standard BS 6840, and IEC 60268-17.
VU meters typically have a range from −20 to +3dB where 0VU is +4dBu for a sine wave at 1kHz. The rise and fall times of the meter are both 300 milliseconds, meaning that if a constant sine wave of amplitude 0 VU is applied suddenly, the meter will take 300 milliseconds to reach the 0 on the scale. It behaves as a full-wave averaging instrument, and is not optimal for measuring peak levels. Its inability to measure peak levels accurately, critical in particular for digital recording, earned it the reputation as a bacronym for 'Virtually Useless'.