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Today there are so many different types of audio measurements to choose from that it can be overwhelming if you let yourself get overwhelmed. The fact is that many of today’s meter options come from the standard analog VU meter, which is much older than you think. To know more about reading audio and how you can measure it you can join any sound engineering academy in India, like Gray Spark Audio Academy, or can join any audio engineering course. (VU Meter – Some Audio Metering History)
How The VU Meter came to be
The standard VU (Volume Unit) meter was designed in 1936 by a joint effort of CBS, NBC, and Bell Labs and was originally called the SVI, or Standard Volume Indicator. Since the scale was calibrated in volume units, the name stuck and became the analog VU meter we’re used to seeing on all kinds of pro analog audio equipment.
The VU meter was relatively cheap to implement, but had some limitations. For one thing, it was quite slow to respond to a signal. This meant that a mix element with fast transients (such as drums or percussion) could produce peaks that were up to 10dB or higher than the meter indicated. The meter was also built to provide RMS (an electronic calculation called Root Mean Square), or the average value of the signal voltage.
The reference level was 0VU, and anything above that was in the red zone and indicated potential overload, which was true for some low-headroom professional gear and not so much for high-headroom pro gear. Later versions of the VU meter also featured a peak LED that lit up when a predetermined transient level was detected. (VU Meter – Some Audio Metering History)
PPM (Peak Program Meter)
Because of these limitations, mixing post-metered broadcasts with faster response has been a desire of many engineers. That meter was the PPM (Peak Program Meter), which actually started developing before the VU meter in 1932. PPM meters didn’t actually measure the peak of the signal, but they were much better at detecting these fast transients than normal VU meters. They were also much more expensive than VU meters, which is one of the reasons why they were never widely used in recording studios.
As solid-state electronics became more advanced and LEDs became cheaper and easier to use, LED segment meters gradually replaced VU meters on all kinds of professional audio equipment. Instead of VU-style ballistics, these new meters behaved more like high-end meters in that they indicated signal level down to 0 headroom (known as 0dBFS for Full Scale) with the red overload indicator we mostly use in the digital domain today. (VU Meter – Some Audio Metering History)
We are just getting started
While the top of the meter scale is usually 0dBFS with an overload indicator above it, the rest of the meter can be calibrated in many different ways that help us monitor the signal in different ways. The most common types of digital meters in use today include signal presence, spike, RMS, K-scale, and LUFS.
Believe it or not, there are other types of audio measurement options available, including five versions of PPM digital measurement, linear, linear extended, and more. They are all designed to do the same thing – tell us the signal level and measure how close it is to overload. The way they are displayed may differ, but they all serve the same purpose.
Believe it or not there are other types of audio metering selections also available, including five versions of digital PPM metering, Linear, Linear Extended, and more. All are designed to do the same thing – tell us the level of the signal, and measure how close to an overload it is. The way this is displayed may be different, but they all serve the same purpose. (VU Meter – Some Audio Metering History)