amplitude
The measure of a sound wave's intensity, perceived as loudness or volume.
In Depth
Amplitude measures how much air pressure a sound wave displaces — larger waves create louder sounds. In music, amplitude corresponds directly to dynamics: a fortissimo passage has greater amplitude than a pianissimo one. Amplitude is measured in decibels (dB), a logarithmic scale where every 10 dB increase represents a tenfold increase in sound intensity.
In recording and audio engineering, amplitude is controlled through gain, volume faders, and compression. Clipping occurs when amplitude exceeds the maximum level a system can handle, creating distortion. The loudness war in popular music — the trend of mastering albums at ever-higher amplitudes — has been controversial because it reduces dynamic range.
The loudest sound ever recorded was the eruption of Krakatoa in 1883, which reached an estimated 310 dB and was heard 4,800 kilometres away. For comparison, a full orchestra at fortissimo reaches about 100 dB.