Vowel discrimination by hearing infants as a function of number of spectral channels

Abstract

Reduced spectral resolution negatively impacts speech perception, particularly perception of vowels and consonant place. This study assessed impact of number of spectral channels on vowel discrimination by 6-month-old infants with normal hearing by comparing three listening conditions: Unprocessed speech, 32 channels, and 16 channels. Auditory stimuli (/ti/ and /ta/) were spectrally reduced using a noiseband vocoder and presented to infants with normal hearing via visual habituation. Results supported a significant effect of number of channels on vowel discrimination by 6-month-old infants. No differences emerged between unprocessed and 32-channel conditions in which infants looked longer during novel stimulus trials (i.e., discrimination). The 16-channel condition yielded a significantly different pattern: Infants demonstrated no significant difference in looking time to familiar vs novel stimulus trials, suggesting infants cannot discriminate /ti/ and /ta/ with only 16 channels. Results support effects of spectral resolution on vowel discrimination. Relative to published reports, young infants need more spectral detail than older children and adults to perceive spectrally degraded speech. Results have implications for development of perception by infants with hearing loss who receive auditory prostheses.

Spectral Ripple Discrimination in Normal-Hearing Infants

“…Measures of frequency resolution, including critical bandwidth and psychophysical tuning curve width, mature by 6 months of age (Olsho et al 1987, Schneider et al 1990, Spetner and Olsho 1990). Despite the fact that infants and young children are particularly reliant on spectral detail for speech discrimination in studies using CI simulations (Warner-Czyz et al 2014, Nittrouer et al 2015), spectral resolution remains immature in NH listeners through 7–10 years of age (Blagosklonova et al 1989, Allen and Wightman 1994, Peter et al 2014). One possible explanation for this is that development of spectral resolution in NH listeners is mainly due to maturation of across-channel intensity resolution.…”

Modified spectral tilt affects infants' native-language discrimination of approximants and vowels

“…Up until now, native-language attunement has been largely shown by a failure to discriminate most non-native contrasts (Best and McRoberts, 2003;Werker and Tees, 1984), but this study, our previous study (Beach and Kitamura, 2011), and other studies of spectrally modified speech (Cabrera et al, 2013;Cabrera et al, 2105;Warner-Czyz, 2014), all demonstrate that a form of attunement also occurs for acoustically modified native speech sounds. It seems that once perceptual reorganization for native speech begins to emerge between 6 and 9 months of age, infants have difficulty discriminating native speech sounds that deviate from the native spectral profile.…”

“…Six-month-olds could discriminate spectrally degraded consonants even when the stimuli contained only 4 channels (Cabrera et al, 2013;Cabrera et al, 2015). However, for vowel contrasts, infants only discriminated unmodified and 32-channel speech, not 16-channel speech, providing further evidence that some attunement to spectrally intact native vowels may be occurring at this age (Warner-Czyz et al, 2014).…”

“…Cabrera et al (2013) and Cabrera et al (2015) showed that 6-month-olds can discriminate vocoded consonants, /b/-/p/ and /b/-/d/, in which the number of channels varied between 4 and 32 and the spectral and temporal information available was systematically degraded. Six-month-olds can also discriminate similarly degraded vowels, /i/-/a/, although they were less able to cope with degraded spectral information when compared to older children and adults (Warner-Czyz et al, 2014).…”

Hearing Threshold of Children with Hearing Screening-Passed in Day Care Center and Speech-Language Pathology Clinic

“…우리나라에서 신생아 난청의 조기 발견과 중재는 체계적으로 시행하고 있으나 [2] 신생아 청각선별을 시행한 이후 생애 불특정 시기에 다양한 원인으로 청력손실이 발생할 수 있다 [3]. 학령기 청소년들은 휴대용 음향기기로 강한 음원을 청취하기도 하고 [4], 성인기에는 직업적 소음을 포함한 다양한 원인으로 청력손실이 생길 수 있다.…”