Phonetic recoding of print and its effect on the detection of concurrent speech in amplitude-modulated noise

When an amplitude-modulated noise generated from a spoken word is presented simultaneously with the word's printed version, the noise sounds more speechlike. This auditory illusion obtained by Frost, Repp, and Katz (1988) suggests that subjects detect correspondences between speech amplitude envelopes and printed stimuli. The present study investigated whether the speech envelope is assembled from the printed word or whether it is lexically addressed. In two experiments subjects were presented with speech-plus-noise and with noise-only trials, and were required to detect the speech in the noise. The auditory stimuli were accompanied with matching or non-matching Hebrew print, which was unvoweled in Experiment 1 and voweled in Experiment 2. The stimuli of both experiments consisted of high-frequency words, low-frequency words, and non-words. The results demonstrated that matching print caused a strong bias to detect speech in the noise when the stimuli were either high- or low-frequency words, whereas no bias was found for non-words. The bias effect for words or non-words was not affected by spelling to sound regularity; that is, similar effects were obtained in the voweled and the unvoweled conditions. These results suggest that the amplitude envelope of the word is not assembled from the print. Rather, it is addressed directly from the printed word and retrieved from the mental lexicon. Since amplitude envelopes are contingent on detailed phonetic structures, this outcome suggests that representations of words in the mental lexicon are not only phonological but also phonetic in character.