05 - Amplitude

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If frequency is the distance between the waves, then amplitude is the height of the waves.

Amplitude is a measure of a sound's energy.

There are several different ways to measure this energy, but in digital sound processing the most commonly used is a number between 0 and 1.

0 is total stillness, 1 is the loudest possible sound before the wave starts to change in unpleasant ways.

sine wave at amplitude 0.1, 0.2 and 0.5

A classical problem with digital sound is that of clipping. This happens when the amplitude goes higher than 1. The computer solves this problem quite simply by hacking off the waveform at amplitude 1, which changes the sound dramatically:

sine wave at amplitude 2

Our sine wave is no longer a sine wave, but something else entirely.

Alternative measure: dBFs

In many sound editing programs you will see the amplitude measured in decibels instead. This is a bit of a weird scale, but it is useful for many purposes which we will get to later in the workshop. In this measuring system we call the loudest possible signal 0 dB, and then we move downwards, all the way to silence at -∞. In most practical applications anything below -70 dB is inaudible.

Amp to dB conversion:

0.1 -> -20.0 dB
0.2 -> -13.9 dB
0.3 -> -10.4 dB
0.4 -> -07.9 dB
0.5 -> -06.0 dB
0.6 -> -04.4 dB
0.7 -> -03.0 dB
0.8 -> -01.9 dB
0.9 -> -00.9 dB
1.0 ->  00.0 dB