Level, also known as amplitude, describes how big the signal is. The greater the amplitude of the signal, the higher the level.
Level is probably the most basic audio measurement we can make: How much energy does our device output? What level can it output before it distorts the signal?
Level can be expressed in several different units. In the analog domain, the most common are volts, watts, dBV, or dBu. The digital domain has its own set of units, which we’ll discuss in a later tutorial. Engineers like to use dB, short for decibel, because it’s a logarithmic unit, so large ranges can be expressed in simple numbers. Though dB by itself is just a ratio between two values, the dB in Level measurements assumes a reference to a defined constant. For example, dBV is referenced to the Volt, where zero dBV equals 1 volt. -1 dBV is one decibel less than 1 volt or 0.89 Volts and -100 dbV is 100 db down from one volt, or 0.00001 Volts.A good rule of thumb is for every extra 6 dB of Level, there’s approximately double the voltage.
dBm has its origins in an old audio standard. Unless you have a good reason to use dBm, the more common unit today is dBu, where zero dBu is equivalent to 0.7746 Volts.
Gain is a very common measurement for amplifiers. It is the device’s output level divided by the level at the input. Being a ratio, it’s usually measured in dB but it could be looked at as a percent.Volume, or loudness, is a subjective concept that relates to the perception of sound by the listener. There are no units for volume, just percentages or reference-less numbers.
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