Shorter duration Lower amplitude Ill-defined formants Differences between vowels and sonorants. Sounds have greater amplitude - on the average, two times the amplitude of obstruents. Sounds have, on the average, half the amplitude of sonorants. Acoustic Characteristics of Vowels Vowels are characterized by the presence of relatively intense and well-defined formants. First three formants are adequate to perceptually discriminate all English vowels.
Energy is concentrated in low frequencies in vowels.
Source spectrum for vowels is a complex periodic sound from the larynx. High vowels have higher f 0 than low vowels because of the elevation of the larynx. F 1 is primarily determined by the back cavity - the size of the cavity behind the tongue hump. The back cavity is larger for the high vowels than for low vowels because, for high vowels, the tongue is pulled forward and up. A larger cavity results in a low F 1 for high vowels.