ABSTRACT
To operate a sound recording or reproducing system properly, some method for determining the signal levels in different parts of the system to avoid overloading, noise, and distortion is required. This is the purpose of the volume indicator (VI) meter. A VI meter is a meter used to measure levels of audio-frequency signals. The term volume indicator is generally associated with meters calibrated in decibels. Until recently, volume unit (VU) meters were devices to measure power with respect to 1 mW of power across a 600 line. Today VU measurements are made with respect to many different bases.
