Duplex perception refers to the linguistic phenomenon whereby "part of the acoustic signal is used for both a speech and a nonspeech percept." A listener is presented with two simultaneous, dichotic stimuli. One ear receives an isolated third-formant transition that sounds like a nonspeech chirp. At the same time the other ear receives a base syllable. This base syllable consists of the first two formants, complete with formant transitions, and the third formant without a transition. Normally, there would be peripheral masking in such a binaural listening task but this does not occur. Instead, the listener's percept is duplex, that is, the completed syllable is perceived and the nonspeech chirp is heard at the same time. This is interpreted as being due to the existence of a special speech