Intrinsic characteristics of sounds are intensity, pitch, duration and spectral composition. Open vowels have a higher intrinsic intensity than closed vowels: the intensity of closed vowels is damped by the shape of the vocal tract (Lehiste & Peterson 1959). Open vowels have a longer intrinsic duration as the jaw must be lowered to produce an open vowel (Peterson & Lehiste 1960). The intrinsic pitch of consonants is always lower than that of neighbouring vowels because the air needed to produce consonants is obstructed on its way out. Consequently, the pressure in the mouth builds up, resulting in a decreased transglottal pressure difference. This reduction in the transglottal pressure difference causes the vocal folds to vibrate more slowly. Vowels also differ in their intrinsic pitch (Lehiste & Peterson 1961). Vowels can be characterised by their specific spectral composition or timbre.
- Lehiste, I. & Peterson, G.E. 1961. Some basic considerations in the analysis of intonation, Journal of the Acoustical Society of America, 33, 419-425
- Lehiste, I. & Peterson, G.E. 1959. Vowel amplitude and phonemic stress in American English, Journal of the Acoustical Society of America, 31, 428-435
- Peterson, G.E. & Lehiste, I. 1960. Duration of syllable nuclei in English, Journal of the Acoustical Society of America, 32, 693-703