Speech perception adjusts to stable spectrotemporal properties of the listening environment

When perceiving speech, listeners compensate for reverberation and stable spectral peaks in the speech signal. Despite natural listening conditions usually adding both reverberation and spectral coloration, these processes have only been studied separately. Reverberation smears spectral peaks across time, which is predicted to increase listeners' compensation for these peaks. This prediction was tested using sentences presented with or without a simulated reverberant sound field. All sentences had a stable spectral peak (added by amplifying frequencies matching the second formant frequency [F2] in the target vowel) before a test vowel varying from /i/ to /u/ in F2 and spectral envelope (tilt). In Experiment 1, listeners demonstrated increased compensation (larger decrease in F2 weights and larger increase in spectral tilt weights for identifying the target vowel) in reverberant speech than in nonreverberant speech. In Experiment 2, increased compensation was shown not to be due to reverberation tails. In Experiment 3, adding a pure tone to nonreverberant speech at the target vowel's F2 frequency increased compensation, revealing that these effects are not specific to reverberation. Results suggest that perceptual adjustment to stable spectral peaks in the listening environment is not affected by their source or cause.