I think the question could best be answered by the analogy: “What’s wrong with wetting your finger to measure wind velocity?”

In truth, the VU meter does a great job of indicating the average level of a constant state signal.

However the VU meter becomes unpredictable when attempting to measure the actual levels involved in a transient passage or in a complex waveform.

Since music is composed of complex waveforms and transient passages a problem in accurate monitoring does exist.

Engineers have been aware of the problem for years and have learned to cope with it.

Engineers had learned that they could depend on instantaneous peak levels to be about 6 to 8 dB higher than that indicated on the VU meter when the program material was orchestral or vocal music.

When engineers were dealing with ordinary performance mixed orchestral or vocal music, on one or two tracks, they simply allowed themselves 10 dB of “headroom” in the electronics, and recorded at a level of 6 dB below the 3% distortion point of the tape.

If a cleaner recording was required, the record level was reduced by another 4 to 6 dB thereby reducing the 3% distortion peaks.

With only one or two tracks, noise was not the problem it is today. Further, the public ear had been conditioned to accept the transient distortion and the tape noise, even if these had not been masked by the noise levels and distortions produced within the available playback equipment.

Today-it’s been happening for about the last five years—we find that our crutches have been kicked out from under us. Each of the following series of events has contributed to the unsuitability of the VU meter as an accurate monitor of levels in modern recording practice.

Multi Track Recording
Today, we are monitoring levels of individual instruments more often than we are monitoring ordinary performance mixed material. Consequently, peak levels do not follow traditional 6 to 8 dB reading error. Take, for instance, a tambourine.

Traditionally, it was buried in the mix someplace and its transient peaks were low enough not to be a serious problem. Now take the same tambourine and put it on a track of its own. Try to record it at “O” level and you will find yourself in big trouble.

Depending on the particular instrument, a specific microphone and the amount of equalization used, you will probably find your VU meter reading to be between 12 and 16 dB off. The only procedure you can follow is to make a calculated guess as to the proper VU reading and go.

If you have guessed too high, the result will be transient distortion and a lack of presence. If the recorded level is too low, you have an excessive amount of noise, which leads to the next modern-day metering problem.

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