Tyco 579-769 specifications Nature of Speech, Speech Pattern that Illustrates Modulations

The Nature of Speech

Introduction	The frequency of speech ranges over seven octaves from 125 Hz to 8,000 Hz, with the majority of
	frequencies contributing to intelligibility falling between 500 Hz and 4,000 Hz. The creation of
	“phonemes,” or the sounds that make up words is created by amplitude modulation of those
	frequencies. Amplitude modulations of speech patterns are seen as the peaks and valleys of the
	waveform. These modulations range from 0.63 Hz to 12.5 Hz. A typical fragment of speech:
	“an emergency has been reported” is shown in the figure below.

Consonants and Vowels

Figure 2-2. Speech Pattern that Illustrates Modulations

Consonants generally have the lowest power contribution to speech, but are extremely important to intelligibility. Consonants like the “T” and “S” sounds are relatively high in frequency, but of a short duration. Vowels (A, E, I, O, U sounds) carry most of the power of the speech signal.

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