The acoustics of fricative consonants

The acoustic mechanism of fricative consonants was studied in the context of three domains: speech, mechanical models. and theoretical models. All fricative configurations have in common a small turbulence-producing constriction within the vocal tract. Thus, preliminary experiments were conducted using a mechanical model having this basic configuration of a constriction in a tube. Parameters such as constriction area. length. location, and degree of inlet tapering, and presence of an obstacle, were varied. It was found that acoustically the most significant parameters are the presence of an obstacle, the length of the front cavity, and the flowrate. Therefore, configurations in which only these parameters were varied, referred to as the obstacle and no-obstacle cases, were examined more thoroughly and modeled theoretically. A source function for the obstacle case was derived from the far-field sound pressure mea-sured when the obstacle was located in space, downstream of a constriction in a baffle. The directivity pattern produced by the obstacle in this position was similar to that of a dipole, as expected. A dipole source located inside a duct is equivalent to a pressure source in a transmnission-lille model, when only the longitudinal modes of a duct are considered. The filter