Abstract:While considerable evidence suggests that bilateral cochlear implant (CI) users' sound localization abilities rely primarily on interaural level difference (ILD) cues, and only secondarily, if at all, on interaural time difference (ITD) cues, this evidence has largely been indirect. This study used head-related transfer functions (HRTFs) to independently manipulate ITD and ILD cues and directly measure their contribution to bilateral CI users' localization abilities. The results revealed a strong reliance on ILD cues, but some CI users also made use of ITD cues. The results also suggest a complex interaction between ITD and ILD cues.

This paper presents a compact graphical method for comparing the performance of individual hearing impaired ͑HI͒ listeners with that of an average normal hearing ͑NH͒ listener on a consonant-by-consonant basis. This representation, named the consonant loss profile ͑CLP͒, characterizes the effect of a listener's hearing loss on each consonant over a range of performance. The CLP shows that the consonant loss, which is the signal-to-noise ratio ͑SNR͒ difference at equal NH and HI scores, is consonant-dependent and varies with the score. This variation in the consonant loss reveals that hearing loss renders some consonants unintelligible, while it reduces noise-robustness of some other consonants. The conventional SNR-loss metric ⌬SNR 50 , defined as the SNR difference at 50% recognition score, is insufficient to capture this variation. The ⌬SNR 50 value is on average 12 dB lower when measured with sentences using standard clinical procedures than when measured with nonsense syllables. A listener with symmetric hearing loss may not have identical CLPs for both ears. Some consonant confusions by HI listeners are influenced by the high-frequency hearing loss even at a presentation level as high as 85 dB sound pressure level.

This article provides a stratified sampling plan for HA research, based on a quantitative analysis of the distribution of PTA and age for HA users. Adopting such a sampling plan will make HA research results more representative and generalizable. In addition, data acquired using such plans can be reinterpreted as the HA population changes.

The present study aimed determining the effect of audibility on a consonant-byconsonant perception and on perceptual confusions per hearing-impaired (HI) listener.Methods: Six participants with sensorineural hearing loss participated. Sixteen consonantvowel (CV) syllables with the common vowel /a/ were presented as a function of signal-tonoise ratio. Gains were computed with subject's hearing thresholds by using National Acoustics' Laboratory -Revised Compensation Rule. Then the gains were applied to each of the 16 CV syllables. Consonant confusions were measured without and with gain.Results: We identified three levels of difficulty in CV perception regardless of applying gain: Easy-