Waveform

A waveform specifies how a wave-related quantity varies with time or position. For an electrical recording it may be $V(t)$, an electric potential difference; for sound it may be the sound pressure $p(t)$. Both the shape and its physical scale matter: a normalized trace alone omits amplitude and time units.

For example,contains a fundamental frequency $f$ and a third harmonic. It has the same period $1/f$ as the first sinusoid but a different shape. Varying the relative phase of the third harmonic changes that shape even when the two component amplitudes stay fixed. A Fourier series describes periodic waveforms through such harmonic amplitudes and phases.

A microphone and oscilloscope can record an acoustic waveform after calibration. The recording is also affected by the instrument's frequency response and signal sampling: a narrow-band microphone smooths sharp features, and inadequate sampling can misrepresent oscillations. The observed waveform therefore represents the signal together with the measurement chain.