Perceptual effects of formant enhancement with the factors of phonetic type, listening conditions and language experience of listeners

The second formant (F2) enhancement is a technique that aims to improve speech perception in adverse noise by amplifying the F2 of speech signals. The current study aimed to investigate whether F2 enhancement would improve speech identification with the factors of phonetic type (e.g., vowel and consonant), listening conditions (e.g., speech and nonspeech noise at moderately and very challenging SNRs), and language experience of listeners (e.g., native and nonnative listeners), if any, whether the amount of perceptual benefit was dependent on these factors. Two groups of participants, English native and nonnative listeners, were recruited in this study. Identification of English vowels and consonants with and without F2 enhancement were measured in quiet, long-term speech shaped noise (LTSSN) and six-talker babble (6-TB) at the signal-to-noise ratios (SNRs) of -10 dB and -15 dB. Overall, significant improvements from F2 enhancement were found in both vowel and consonant identification for both native and nonnative listeners in various listening conditions. Furthermore, greater improvement was found at the SNR of -15 dB than at the SNR of -10 dB, as well as for nonnative listeners than native listeners in vowel identification. Meanwhile, the amount of benefit was generally comparable speech and nonspeech noise. These results indicate that F2 enhancement could improve phonetic identification in noise for native and nonnative listeners, showing a potential as a speech enhancement algorithm in challenging noise.