This paper presents computational results of sound pressure distributions and transfer characteristics for a large number of vocal-tract models which contain geometrical perturbations. A small change of the vocal-tract shape is regarded as a geometrical perturbation of the axis position of each vocal-tract section. Computation of the acoustic field in the models are performed using higher-order modes. The results indicate that acoustic characteristics in the higher frequencies are highly sensitive to the small change of the vocal-tract shape.