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. | ||
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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.
