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Rollover effect of signal level on vowel formant discrimination.

The goal of this study was to measure the ability of normal-hearing listeners to discriminate formant frequency for vowels in isolation and sentences at three signal levels. Results showed significant elevation in formant thresholds as formant frequency and linguistic context increased. The signal level indicated a rollover effect, especially for F2, in which formant thresholds at 85 dB SPL were lower than thresholds at 70 or 100 dB SPL in both isolated vowels and sentences. This rollover level effect could be due to reduced frequency selectivity and forward/backward masking in sentence at high signal levels for normal-hearing listeners.