Elderly listeners' identification of Japanese long vowel pair `obasan' and `obaasan' using pitch and duration

Japanese has long and short vowel distinction. While duration is the primary cue for listeners, pitch is being used as the secondary cue when duration becomes ambiguous. Duration however is affected by phonetic environment and therefore pitch cues may be more important in daily conversations. At the same time, ageing is known to affect speech recognition, in particular, pitch contour discrimination, such as tones. The current study compared a group of 15 young listeners with 14 elderly listeners using the words `obasan (aunt)' and `obaasan (grandmother),' manipulated in six steps duration-wise and pitch-wise. We found elderly listeners to use pitch more than the young listeners at the duration extremes, suggesting a generational effect on acceptability in accents (or lack of). At the same time, we observed half the elderly listeners to be less sensitive to pitch when duration becomes unreliable, depending on their fundamental frequency difference limens. The more sensitive elderly listeners, who performed similarly to the younger participants, significantly differed in their perception results from the less sensitive elderly listeners. This suggests that pitch deficits are present in half of the near-normal hearing elderly group, contributing to their inability to use pitch cues as well as their younger counterpart.