English Pronunciation Index


Strong and Weak Fricatives :

Fricatives and plosives are obstruent speech sounds because they involve the partial or total blocking of the vocal tract somewhere along its length. This is in contrast to all other speech sounds, which are grouped as the sonorants. Only the obstruents can be either voiced or voiceless; all sonorants are voiced except in unusual cases such as whispering or devoicing because of neighboring devoiced sounds.

Fricatives involve only partial blocking of the vocal tract, but the opening at the point of maximum constriction is so narrow that turbulence patterns develop from the passage of air through the constriction. This turbulence is what we call frication. The strength of frication is determined by the place of frication as well as the energy of the airstream flowing through the opening. The strong fricatives s z S Z have more energy than the weak fricatives v f D T for two reasons. First, there is tighter constriction between the tongue and the alveolar ridge (s, z) or the palato-alveolar region (S, Z) in the strong fricatives than there is between the tongue and the teeth (T, D) or the teeth and the lips (f, v) in the weak fricatives. Second, the turbulent jets of air from the (palato-)alveolar fricatives strike the back of the teeth and result in high-energy sibilance; in the weak fricatives the jets of frication emerge directly into the air around the speaker's mouth without any further modification. You can expect the strong fricatives to show up more clealy on the spectrogram. Clues for weak fricatives will be more subtle. Word initial weak fricatives may also look very much like plosives in continuous speech, expecially f, D, and T. This ``stop-like'' production does not seem to affect the strong fricatives.