Can the spectral representation of the auditory peripheral system explain vowel production changes under noises masking lower formants?

This study examines how auditory spectral representations in the peripheral auditory system explain changes in vowel production under noisy conditions, especially when lower formants (F1 and F2) are masked. Ten adult male Japanese speakers produced sustained vowels /a/ and /i/ under quiet and noisy conditions involving three noise types (broadband, low-pass, and high-pass) at 75 and 85 dB. We analyzed vocal intensity and the amplitudes and frequencies of the F1 and F2. Auditory spectral representations, simulated using a loudness model, were used to estimate excitation patterns in the auditory periphery. Most noise conditions significantly increased vocal intensity and the amplitude of both formants. F1 frequency consistently shifted upward under high-intensity broadband noise, while F2 shifts depended on vowel and noise type, shifting upward for /a/ and downward for /i/. Some patterns could not be explained by power spectra alone. Instead, they were better accounted for by frequency-specific masking effects, reflected in overlapping excitation patterns in the auditory spectral representation. These overlaps indicated reduced self-audibility in specific frequency bands, triggering compensatory adjustments. The findings highlight how auditory masking influences speech production, supporting a perceptually grounded model of auditory-motor control in noisy environments.