Background noise interacts with spectral context effects during speech categorization

This is the authors' abstract. We don't add key points for this paper.

Speech perception is heavily influenced by surrounding sounds. When spectral properties differ between earlier (context) and later (target) sounds, this can produce spectral contrast effects (SCEs) that bias categorization of later sounds. For example, context sounds with a low-F1 bias produce more high-F1 responses to the target vowel and vice versa. SCEs have been studied for decades but only for speech perception in quiet. Background noise is expected to interfere with these effects, but the extent of this interference is unclear. On each trial, listeners heard a context sentence and target vowel both combined with speech-shaped noise. Sentences were filtered to add a + 20-dB spectral peak at low-F1 (100–400 Hz) or high-F1 frequencies (550–850 Hz). Target vowels varied from /ɪ/ to /ɛ/. Background noise was unmodulated or sinusoidally modulated at 2/4/8 Hz at variable SNRs. In general, SCEs were larger at better SNRs and in unmodulated noise, but all SCEs were smaller than those reported for speech in quiet. Complex patterns of results were observed at different noise modulation rates, with likely ties to modulations in F1 frequency regions in the context sentence. In sum, background noise diminishes context effects in speech perception, but the extent depends on noise characteristics.