Effects of semitone shifts and sex-mismatched maskers on speech perception of low-frequency Malayalam PB words

Abstract Background Speech perception in noisy environments is significantly influenced by a listener’s ability to segregate competing auditory streams, a process in which fundamental frequency (F0) plays a crucial role, particularly under informational masking conditions. F0 differences, quantified in semitone shifts, facilitate stream segregation by enhancing perceptual distinctiveness between target and masker signals. Although this phenomenon has been extensively studied in various languages, there is limited research on its effects in Malayalam, a Dravidian language characterized by rich prosodic features. The present study investigated how semitone-based variations in F0 affect the perception of low-frequency PB Malayalam words in the presence of gender-specific speech maskers. Twenty-seven young adults (13 males, 14 females) aged 18 to 25 years, all native Malayalam speakers with normal hearing sensitivity, participated in the study. An adaptive SNR-50 paradigm was employed to assess speech perception across eight experimental conditions involving four semitone shifts (0, 4, 8, and 12 ST) and two-talker babble maskers of either male or female voices. Stimuli were presented binaurally, and participants completed a closed-set image selection task to indicate their responses. Results Significant main effects were observed for masker gender, with better performance in the different-gender (male) masker condition. Although semitone shifts alone did not yield significant differences, a significant interaction between semitone and masker gender was noted. Performance was consistently highest at 0 ST across both masker types. Conclusion These findings suggest that while increased F0 separation can aid speech perception, voice naturalness at 0 ST may offer greater perceptual stability. Results have implications for understanding pitch-based stream segregation in Malayalam and improving clinical speech perception strategies.