32. The system of claim 18 , wherein the replacement module replaces each vocal tract transfer function with a different replacement sound transfer function.
18. A system for reducing speech intelligibility while preserving environmental sounds, the system comprising: a receiving module for receiving an audio signal; a voicing detector for processing the audio signal to separate a vocalic region that comprises vowels; a computation module for computing a representation of at least the vocalic regions, the representation including at least a vocal tract transfer function and an excitation; a replacement module for replacing the vocal tract transfer function of the vocalic region with a replacement vocal tract transfer function of a replacement sound to create a modified vocal tract transfer function; and an audio synthesizer for synthesizing a modified audio signal of at least the vocalic region from the modified vocal tract transfer function and the excitation.