![]() The non-sinusoidal shape shows it is complex. This triangle wave has the same 0.01sec cycle duration and 100Hz frequency as the sine wave example.Figure 2 Illustrates another basic waveform, this time triangular.It was Jean-Baptiste Fourier (1768-1830) who discovered that any periodic function can be expressed as the sum of sine functions. A waveform that differs from sinusoidal is complex, composed of more than just a simple tone.This is a tone near the bottom of a the bass singing range or near the bottom of the adult male speaking range. Comparing a cycle of this example to the time scale shows its duration to be 0.01 secs, corresponding to a frequency of 100Hz. Now look at the shape of the wave, sinusoidal, the same shape as that of the sine function.The sound pressure rises and falls above and below the atmospheric pressure (0 on the sound pressure scale), alternating between denser and thinner, between compression and rarefaction.The unit of pressure is Pascal, but the true Pascal values can only be shown for a recording when that recording has been calibrated. This is also what you will see when you look at the waveform of a recording in Praat. The values of the sound pressure scale (-1 to +1) are arbitrary.Figure 1 illustrates the waveform of the simplest type of sound, consisting of just one tone, with no other sound mixed in.You should be familiar with waveform diagrams, if not, see Understanding waveforms.This page introduces some basic geometric waveforms, that have known properties and are useful to remember when studying actual speech (and especially synthesizing speech).Comparison: sine, triangle, sawtooth, pulse.
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