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Praat is software for analyzing, synthesizing, annotating and manipulating speech, created by Paul Boersma and David Weenink. It makes the connection between a recorded acoustic signal and measurable speech properties explicit: a waveform, a spectrogram, a pitch contour and estimated formants describe different aspects of the same recording.^[ref]

For a sustained vowel, one can compare the repeating structure of the waveform with the estimated fundamental frequency, then examine how the frequency spectrum is shaped by the vocal tract. A change in vowel quality need not be a change in pitch. Annotations can align intervals with phonemes or syllables without treating every acoustic boundary as an unambiguous linguistic boundary.

Measurements depend on the analysis settings and the signal. In particular, a displayed pitch contour can contain octave errors, while estimated formants depend on the analysis model. Inspecting the recorded sound and analysis assumptions is therefore part of the experiment, rather than accepting every displayed trajectory as ground truth.

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.