The periodicity of this example comes from the glottal vibrations of the voice.For practical purposes, this is nevertheless regarded as periodic, loosely if you wish, or quasiperiodic. They’re superficially similar but they differ in various details. The strict criterion of periodicity is the repetition of identical activy, something that rarely, if ever, happens in speech.The waveform of three cycles from the vowel sampled at time B in Fig. Figure 3 shows a few cycles from the vowel sampled at time B in Fig.The waveform of the Swedish phrase som vi (that we …) spoken by a radio newsreader Figure 2 shows a speech example from Swedish:įigure 2. In contrast, the waveform of speech is complex and variable, reflecting the variety of vowels and consonants that are used and the dynamic nature of speech articulation with one or more articulators usually in motion at any time (see examples in the What is coarticulation? section).A wave that repeats like this is said to be periodic, and the smallest repeating segment of the wave is the cycle. 1 also appears to be repetitive as it alternates between compression and rarefaction. The sine wave is one example of a number of basic waveforms with known properties that are described in the Standard waveforms tutorial. As soon as the shape of the waveform differs from sinusoidal, it is no longer a simple tone but a complex sound with more than one component. This gives a special meaning to simple tone. This one is sinusoidal, it happens to be exactly the same shape as that of the sine function. Now look at the shape of the wave in Fig.The standard unit of pressure is Pascal, but the true Pascal values can only be shown for a recording when it has been calibrated for measuring Pascal. This is also what you will see when you look at the waveform of a speech recording in Praat. The values of the sound pressure scale (-1 to +1) are arbitrary. The sound pressure scale goes from positive to negative to accommodate that alternation.The sound pressure rises and falls above and below the atmospheric pressure – alternating between denser and thinner, between compression and rarefaction.Not just any pressure, but the sound pressure of this particular tone relative to the atmospheric pressure, which is 0 sound pressure. So the diagram is showing how pressure varies with time.The vertical scale represents sound pressure, the horizontal scale represents time.But it only needs one other tiny sound component added to it, and it’s no longer a simple tone. Whistling or some birdcalls are possible examples. It’s not easy to find a natural simple tone. Theoretically, this is the sound of a tuning fork. Simplest, that is, in the sense that it consists of just one tone, with no other sound mixed in. Figure 1 illustrates the waveform of the simplest type of sound.Standard waveforms with known properties.This page deals with the basic features of waveform diagrams
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