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Speech Articulation and Intelligibility

July 13th Fact-of-the-Day

The audio bandpass of communication systems can be limited where the objective is merely to communicate regardless of perceived sound quality. Consonants contribute the most to intelligibility, but have weak amplitudes compared to much strong vowels. Vowel energy is concentrated primarily in the lower frequencies, so restricting low frequencies increases the consonant-to-vowel amplitude ratio, increasing articulation and intelligibility where signals are masked by noise. Note that articulation and intelligibility are not equivalent. Practical tests have shown that on average 30 percent syllable articulation permits 90 percent full-sentence intelligibility. Tests also have shown that removing all frequencies below 200 Hz has almost no effect on intelligibility, while reducing average speech power 20 percent. If the speech power is then amplified to restore the original level, articulation and intelligibility both improve compared to unprocessed speech. The penalty for that improvement is lower perceived sound quality. ©2005 Martek, International. All rights reserved.

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