Effects of Spectral Resolution and Frequency Mismatch on Speech Understanding and Spatial Release From Masking in Simulated Bilateral Cochlear Implants
Effects of Spectral Resolution and Frequency Mismatch on Speech Understanding and Spatial Release From Masking in Simulated Bilateral Cochlear Implants
复制标题
DOI：
10.1097/aud.0000000000000865
复制
发表时间：
2020-09-01
期刊：
影响因子：
3.7
通讯作者：
Fu, Qian-Jie
中科院分区：
文献类型：
--
作者：
Xu, Kevin;Willis, Shelby;Fu, Qian-Jie
目标：由于耳间频率不匹配，双侧人工耳蜗 (CI) 用户可能不太能够利用正常听力 (NH) 听者用于空间听觉的双耳线索，例如耳间时间差异和耳间声级差异。因此，即使目标说话者和竞争说话者在空间上分开，双边 CI 用户也很难区分竞争语音。本研究的目的是评估频谱分辨率、音调不匹配（分配给植入耳内 CI 电极的声学中心频率与预期螺旋神经节特征频率之间的频率不匹配）和耳间不匹配（每只耳朵音调不匹配程度的差异）对在聆听双边声码器模拟的 NH 受试者中存在竞争说话者的情况下的语音理解和空间掩蔽释放 (SRM) 的影响。设计：在测试过程中，目标语音和掩蔽语音均以五个单词的句子呈现，语法相同，但不一定有意义。这些句子由固定顺序的五个类别（名称、动词、数字、颜色和衣服）组成，每个类别有 10 个项目，这样可以通过从每个类别中随机选择一个单词来生成多个句子。测量了竞争性语音掩蔽器中呈现的目标句子的语音接收阈值（SRT）。目标语音被传送到双耳，并且两个语音掩蔽器被传送到（1）双耳（双耳掩蔽器），或（2）不同的耳朵（双耳掩蔽器：一个传送到左耳，另一个传送到右耳）。刺激包括未处理的语音和四个具有不同耳间失配（0、1 和 2 毫米）的 16 通道正弦声码器模拟。 SRM 计算为白痴和双耳听力条件之间的差异。结果：对于未经处理的语音，双歧和双歧掩蔽器的 SRT 分别为 0.3 和 -18.0 dB。对于具有轻度音调不匹配且无耳间不匹配的频谱退化语音，双耳和双耳掩蔽器的 SRT 分别为 5.6 和 -2.0 dB。当双耳的音调不匹配增加时，双耳和双耳掩蔽器的 SRT 分别恶化至 8.9 和 2.4 dB。当两只耳朵具有不同的音调不匹配（例如，存在耳间不匹配）时，双耳掩蔽器的 SRT 性能下降比双耳掩蔽器大得多。在未处理的语音中观察到最大的 SRM (18.3 dB)。通过 CI 模拟，即使有轻微的音调不匹配但没有耳间不匹配，SRM 也显着降低至 7.6 dB；随着耳间不匹配的增加，SRM 进一步降低。结论：结果表明，在双侧 CI 模拟中，频率分辨率、音调不匹配和耳间不匹配对语音理解和 SRM 具有不同的影响。最大限度地减少耳间不匹配对于优化双耳优势并提高竞争语音（典型的聆听环境）的 CI 性能至关重要。 SRM（双耳和双耳掩蔽器之间的 SRT 差异）可能是一种有用的临床工具，可用于评估双耳 CI 用户的耳间频率不匹配，并评估最大限度减少耳间不匹配的优化方法的益处。
Objectives: Due to interaural frequency mismatch, bilateral cochlear-implant (CI) users may be less able to take advantage of binaural cues that normal-hearing (NH) listeners use for spatial hearing, such as interaural time differences and interaural level differences. As such, bilateral CI users have difficulty segregating competing speech even when the target and competing talkers are spatially separated. The goal of this study was to evaluate the effects of spectral resolution, tonotopic mismatch (the frequency mismatch between the acoustic center frequency assigned to CI electrode within an implanted ear relative to the expected spiral ganglion characteristic frequency), and interaural mismatch (differences in the degree of tonotopic mismatch in each ear) on speech understanding and spatial release from masking (SRM) in the presence of competing talkers in NH subjects listening to bilateral vocoder simulations. Design: During testing, both target and masker speech were presented in five-word sentences that had the same syntax but were not necessarily meaningful. The sentences were composed of five categories in fixed order (Name, Verb, Number, Color, and Clothes), each of which had 10 items, such that multiple sentences could be generated by randomly selecting a word from each category. Speech reception thresholds (SRTs) for the target sentence presented in competing speech maskers were measured. The target speech was delivered to both ears and the two speech maskers were delivered to (1) both ears (diotic masker), or (2) different ears (dichotic masker: one delivered to the left ear and the other delivered to the right ear). Stimuli included the unprocessed speech and four 16-channel sine-vocoder simulations with different interaural mismatch (0, 1, and 2 mm). SRM was calculated as the difference between the diotic and dichotic listening conditions. Results: With unprocessed speech, SRTs were 0.3 and -18.0 dB for the diotic and dichotic maskers, respectively. For the spectrally degraded speech with mild tonotopic mismatch and no interaural mismatch, SRTs were 5.6 and -2.0 dB for the diotic and dichotic maskers, respectively. When the tonotopic mismatch increased in both ears, SRTs worsened to 8.9 and 2.4 dB for the diotic and dichotic maskers, respectively. When the two ears had different tonotopic mismatch (e.g., there was interaural mismatch), the performance drop in SRTs was much larger for the dichotic than for the diotic masker. The largest SRM was observed with unprocessed speech (18.3 dB). With the CI simulations, SRM was significantly reduced to 7.6 dB even with mild tonotopic mismatch but no interaural mismatch; SRM was further reduced with increasing interaural mismatch. Conclusions: The results demonstrate that frequency resolution, tonotopic mismatch, and interaural mismatch have differential effects on speech understanding and SRM in simulation of bilateral CIs. Minimizing interaural mismatch may be critical to optimize binaural benefits and improve CI performance for competing speech, a typical listening environment. SRM (the difference in SRTs between diotic and dichotic maskers) may be a useful clinical tool to assess interaural frequency mismatch in bilateral CI users and to evaluate the benefits of optimization methods that minimize interaural mismatch.