Amplitude

In audio system measurements, telecommunications and others where the measurand is a signal that swings above and below a reference value but is not sinusoidal, peak amplitude is often used.

In electrical engineering, the usual solution to this ambiguity is to measure the amplitude from a defined reference potential (such as ground or 0 V).

With appropriate circuitry, peak-to-peak amplitudes of electric oscillations can be measured by meters or by viewing the waveform on an oscilloscope.

For complicated waveforms, especially non-repeating signals like noise, the RMS amplitude is usually used because it is both unambiguous and has physical significance.

[6] For alternating current electric power, the universal practice is to specify RMS values of a sinusoidal waveform.

The peak-to-peak value is used, for example, when choosing rectifiers for power supplies, or when estimating the maximum voltage that insulation must withstand.

Some common voltmeters are calibrated for RMS amplitude, but respond to the average value of a rectified waveform.

Pulse amplitude is measured with respect to a specified reference and therefore should be modified by qualifiers, such as average, instantaneous, peak, or root-mean-square.

A more general representation of the wave equation is more complex, but the role of amplitude remains analogous to this simple case.

[8] Percussive amplitude envelopes are characteristic of various impact sounds: two wine glasses clinking together, hitting a drum, slamming a door, etc.

Percussive amplitude envelopes model many common sounds that have a transient loudness attack, decay, sustain, and release.