Miyamae Ryosuke, Nishimura Tadashi, Hosoi Hiroshi, Saito Osamu, Shimokura Ryota, Yamanaka Toshiaki, Kitahara Tadashi
Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan.
Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan.
Auris Nasus Larynx. 2017 Feb;44(1):26-32. doi: 10.1016/j.anl.2016.03.002. Epub 2016 Mar 26.
By attaching a transducer to the aural cartilage a relatively loud sound is audible even with a negligibly small fixation pressure applied to the transducer. This form of conduction is referred to as cartilage conduction (CC). Utilizing CC, novel audio devices can be developed, and one possible application is a CC hearing aid. However, there are no studies on speech perception in CC. In this study, CC speech recognition performance was measured and compared with that for air and bone conduction (AC and BC, respectively).
Nine volunteers with normal hearing participated in the study. The performance-intensity functions were measured for AC, BC and CC. These measurements were performed in the conditions with and without an earplug.
Without the earplug, no differences in speech recognition scores were observed among AC, BC, and CC. With the earplug, the level at which the maximum speech recognition score was obtained did not increase in CC, which agreed with the result of BC but not AC. The maximum speech recognition CC score decreased with the earplug. The performance-intensity functions for AC and BC shifted in parallel with the earplug. These shifts approximated the average threshold shifts. In contrast, for CC, the performance-intensity function did not shift in parallel with the earplug. As for the CC threshold shifts with the earplug, although the threshold at 500Hz decreased by 15.4dB, those at 2000 and 4000Hz increased by 13.8 and 31.1dB, respectively. Compared with AC and BC, CC excessively emphasized low over high frequency sounds when the earplug was inserted. Confusion matrices analysis demonstrated that 4%, 22%, and 74% of the errors occurred at low, intermediate, and high frequency speech sounds, respectively. Thus, this excessive low frequency sound emphasis probably prevented the recognition of high frequency speech sounds.
The decrease in the maximum speech recognition score for CC with the earplug was derived from the biased frequency composition. It can be improved by frequency composition adjustment.
通过将换能器附着于耳软骨，即使对换能器施加极小的固定压力，也能听到相对较大的声音。这种传导形式被称为软骨传导（CC）。利用CC，可以开发新型音频设备，一种可能的应用是CC助听器。然而，目前尚无关于CC中语音感知的研究。在本研究中，测量了CC语音识别性能，并与气导和骨导（分别为AC和BC）的语音识别性能进行了比较。
9名听力正常的志愿者参与了本研究。测量了AC、BC和CC的性能-强度函数。这些测量在有和没有耳塞的条件下进行。
在没有耳塞的情况下，AC、BC和CC之间的语音识别分数没有差异。使用耳塞时，CC中获得最大语音识别分数的水平没有增加，这与BC的结果一致，但与AC不同。CC的最大语音识别分数随着耳塞而降低。AC和BC的性能-强度函数随着耳塞平行移动。这些移动近似于平均阈值移动。相比之下，对于CC，性能-强度函数没有随着耳塞平行移动。至于使用耳塞时CC的阈值移动，虽然500Hz处的阈值降低了1５.4dB，但2000Hz和4000Hz处的阈值分别增加了13.8dB和31.1dB。与AC和BC相比，插入耳塞时CC过度强调低频声音而非高频声音。混淆矩阵分析表明，分别有4%、22%和74%的错误发生在低频、中频和高频语音声音上。因此，这种对低频声音的过度强调可能阻碍了高频语音声音的识别。
使用耳塞时CC的最大语音识别分数下降是由于频率成分偏差所致。通过调整频率成分可以改善这一情况。
