A Volume Unit Meter. The VU Meter is the device in music studios with the delayed bouncing needle and it is used to measure the overall volume of the sound. The VU Meter was designed by Bell Labs for testing phone lines. In 1939 in conjunction with NBC and ABC a modified VU meter for broadcasting was developed. Rather then measuring the peak of the audio level the VU meter gives an average level of the signal. The idea behind this is that it emulates the human ear closer then something that measures only the peaks (Though this was not the reason it was developed). You use a VU Meter in conjunction with Peak Programme Meter (PPM) when finding the appropriate levels for audio recording.