Pieper Sabrina H, Bahmer Andreas
Clinic for Otolaryngology, Comprehensive Hearing Center, University of Würzburg , Würzburg 97080 , Germany.
Cochlear Implants Int. 2019 Nov;20(6):312-323. doi: 10.1080/14670100.2019.1656847. Epub 2019 Aug 25.
The rate pitch discrimination ability of cochlear implant (CI) users is poor compared to normal-hearing (NH) listeners. At low pulse rates, the just noticeable difference (JND) is on average 20% of the base rate, while NH listeners can discriminate small frequency differences of 0.2% at 1 kHz. Recent investigations suggest that double pulses with short interpulse intervals (IPIs) may have a beneficial effect on rate pitch discrimination in CI users. In a first experiment psychophysical tests were carried out to establish whether rate pitch in CI users could be improved by applying double pulses with equal amplitude and short IPIs. Pulse trains with base rates of 200 and 400 pps, composed of either single pulses or double pulses with IPIs of 15, 50, and 150 μs were presented. In a second experiment pairwise comparisons were carried out between pitch of a pulse train composed of alternating double and single pulses with pitch of pulse trains composed of single pulses. The alternating pulse train had a base rate of 400 pps, the pulse trains with solely single pulses had base rates of 200, 300, and 400 pps. The loudness and pitch perception of the different stimulus types were evaluated and compared. A significant loudness difference was found between single and double pulses for both pulse rates. The JND for pitch discrimination between double-pulse IPIs had a high inter-subject variability, and no significant group effect was found. No subject reported a pitch change between double pulse and single pulse stimulation. In contrast, most of the subjects recognized a change in pitch between single-pulse trains and pulse trains with alternating double and single pulses. The latter was lower in pitch than the single-pulse train stimulation. To conclude, using (equal amplitude) double pulses instead of single pulses in a pulse train does not effect pitch perception. Instead, loudness differs between double pulses and single pulses with the same amplitude.
与听力正常（NH）的听众相比，人工耳蜗（CI）使用者的速率音调辨别能力较差。在低脉冲率下，恰可察觉差（JND）平均为基础率的20%，而NH听众在1kHz时能够辨别0.2%的小频率差异。最近的研究表明，具有短脉冲间隔（IPI）的双脉冲可能对CI使用者的速率音调辨别有有益影响。在第一个实验中，进行了心理物理学测试，以确定通过应用等幅且IPI短的双脉冲是否可以改善CI使用者的速率音调。呈现了基础率为200和400pps的脉冲序列，其由单脉冲或IPI为15、50和150μs的双脉冲组成。在第二个实验中，对由交替双脉冲和单脉冲组成的脉冲序列的音高与由单脉冲组成的脉冲序列的音高进行了成对比较。交替脉冲序列的基础率为400pps，仅由单脉冲组成的脉冲序列的基础率为200、300和400pps。对不同刺激类型的响度和音高感知进行了评估和比较。对于两种脉冲率，单脉冲和双脉冲之间均发现了显著的响度差异。双脉冲IPI之间的音高辨别JND具有较高的个体间变异性，未发现显著的组效应。没有受试者报告双脉冲和单脉冲刺激之间的音高变化。相比之下，大多数受试者识别出单脉冲序列与交替双脉冲和单脉冲的脉冲序列之间的音高变化。后者的音高低于单脉冲序列刺激。总之，在脉冲序列中使用（等幅）双脉冲而非单脉冲不会影响音高感知。相反，相同幅度的双脉冲和单脉冲之间响度不同。
