A broadband dynamic transducer is used to apply a continuous acoustic excitation at the lips for purposes of measuring the vocal tract area function. A pair of closely spaced microphones inside the tube that conveys this excitation signal is used to resolve forward and backward going acoustic wave components. The reflection coefficients of the vocal tract are obtained by a migration operator which transforms wave components measured at the lips into the equivalent causal response to a finite duration wavelet incident at successive depths into the vocal tract. The accuracy of this measurement technique is influenced by (1) the bandwidth limit imposed by the separation of the microphone pair, (2) the stability of microphone gain, and (3) the sensitivity of the microphones to structure borne vibrations. The combined influence of these limits on accuracy is determined experimentally by making acoustic measurements of the area functions of epoxy molds made to the dimensions of vowels derived from Fant's x‐ray data. [Work supported by NIH grants NS 2156 and NS 16377.]