Acoustic properties of phonemes in continuous speech for different speaking rate

An investigation has been made for individual phonemes focusing mainly on their duration in continuous speech spoken at different rates: fast, normal, and slow. Fifteen short sentences uttered by four male speakers have been used as the speech material which comprises a total of 291 morae. The normal speaking rate (n-speech) is, on average, 150 milliseconds/mora (or 300 morae/minute) and the four speakers were asked to read the sentences twice as fast as (f-speech) and half as slow as (s-speech) the normal speed in reference to n-speech. Among consonants, the greatest influence has been found to occur on the syllabic nasal /N/ and the least on the voiceless stop /t/ in f-speech. For s-speech, /N/ has also been found to be the greatest but the least is voiced stop /d/. The ratio of duration between consonant and vowel of a CV-syllable in f-speech is kept almost the same as that in n-speech while vowel lengthening becomes significantly large in s-speech.