Absence of ear advantage for segmental and tonal perception in noise

Abstract

When different speech sounds are presented to the left and right ear simultaneously, right-handed listeners usually score higher for identifying stimuli presented to the right ear, reflecting the left hemisphere dominance for speech perception. Recently, the right hemisphere was proposed to contribute more than the left hemisphere for speech perception in an acoustically noisy environment. For testing this hypothesis, 40 right handed native Cantonese speakers were recruited for dichotic listening tests. Paired syllables were presented to participants in quiet and in noise (signal to noise ratio were set to 0 dB and -10 dB in two separate conditions). The two syllables in each pair differed from each other in consonant, vowels, or tones. Participants were asked to verbally repeat the syllable they thought was clearer. Accuracy rate was calculated for each ear. For the quiet condition, the mean accuracy rate was significantly higher for syllables presented to the right ear than those presented to the left ear for consonants, vowels, and tones. Whereas for both noise conditions, no significant ear advantage was found. The absence of ear advantage in noise suggested that the right hemisphere contributes more in a noisy environment than in quiet for both segmental and tonal perception.