Department of Hearing and Speech Sciences, University of Maryland, College Park, Maryland, USA.
Neuroscience and Cognitive Science Program, University of Maryland, College Park, Maryland, USA.
Ear Hear. 2020 Sep/Oct;41(5):1236-1250. doi: 10.1097/AUD.0000000000000842.
When auditory and visual speech information are presented together, listeners obtain an audiovisual (AV) benefit or a speech understanding improvement compared with auditory-only (AO) or visual-only (VO) presentations. Cochlear-implant (CI) listeners, who receive degraded speech input and therefore understand speech using primarily temporal information, seem to readily use visual cues and can achieve a larger AV benefit than normal-hearing (NH) listeners. It is unclear, however, if the AV benefit remains relatively large for CI listeners when trying to understand foreign-accented speech when compared with unaccented speech. Accented speech can introduce changes to temporal auditory cues and visual cues, which could decrease the usefulness of AV information. Furthermore, we sought to determine if the AV benefit was relatively larger in CI compared with NH listeners for both unaccented and accented speech.
AV benefit was investigated for unaccented and Spanish-accented speech by presenting English sentences in AO, VO, and AV conditions to 15 CI and 15 age- and performance-matched NH listeners. Performance matching between NH and CI listeners was achieved by varying the number of channels of a noise vocoder for the NH listeners. Because of the differences in age and hearing history of the CI listeners, the effects of listener-related variables on speech understanding performance and AV benefit were also examined.
AV benefit was observed for both unaccented and accented conditions and for both CI and NH listeners. The two groups showed similar performance for the AO and AV conditions, and the normalized AV benefit was relatively smaller for the accented than the unaccented conditions. In the CI listeners, older age was associated with significantly poorer performance with the accented speaker compared with the unaccented speaker. The negative impact of age was somewhat reduced by a significant improvement in performance with access to AV information.
When auditory speech information is degraded by CI sound processing, visual cues can be used to improve speech understanding, even in the presence of a Spanish accent. The AV benefit of the CI listeners closely matched that of the NH listeners presented with vocoded speech, which was unexpected given that CI listeners appear to rely more on visual information to communicate. This result is perhaps due to the one-to-one age and performance matching of the listeners. While aging decreased CI listener performance with the accented speaker, access to visual cues boosted performance and could partially overcome the age-related speech understanding deficits for the older CI listeners.
当听觉和视觉语音信息同时呈现时，与仅听觉（AO）或仅视觉（VO）呈现相比，听者会获得视听（AV）增益或语音理解的提高。接受语音输入质量下降的人工耳蜗（CI）使用者主要通过时间信息来理解语音，他们似乎可以轻松利用视觉线索，并获得比正常听力（NH）使用者更大的 AV 增益。然而，当尝试理解带有口音的言语与非带口音的言语时，对于 CI 使用者来说，AV 增益是否仍然相对较大，目前尚不清楚。带口音的言语会导致时间听觉线索和视觉线索发生变化，从而降低 AV 信息的有用性。此外，我们还试图确定对于非带口音和带西班牙口音的言语，CI 使用者相对于 NH 使用者的 AV 增益是否相对较大。
通过在 AO、VO 和 AV 条件下向 15 名 CI 和 15 名年龄和表现匹配的 NH 使用者呈现英语句子，研究了非带口音和带西班牙口音的言语的 AV 增益。通过改变 NH 使用者噪声声码器的声道数量来实现 NH 和 CI 使用者之间的表现匹配。由于 CI 使用者的年龄和听力史存在差异，因此还检查了与听者相关的变量对语音理解表现和 AV 增益的影响。
在非带口音和带口音条件下，以及在 CI 和 NH 使用者中均观察到了 AV 增益。两组使用者在 AO 和 AV 条件下的表现相似，而带口音条件下的归一化 AV 增益相对于非带口音条件下的增益较小。在 CI 使用者中，与非带口音的说话者相比，年龄较大与带口音的说话者的表现明显较差相关。通过利用 AV 信息显著提高表现，一定程度上减轻了年龄的负面影响。
当听觉语音信息因 CI 声音处理而恶化时，即使存在西班牙口音，视觉线索也可用于提高语音理解。与呈现声码化语音的 NH 使用者相比，CI 使用者的 AV 增益非常匹配，这是出乎意料的，因为 CI 使用者似乎更依赖视觉信息进行交流。这一结果可能归因于使用者的年龄和表现的一对一匹配。虽然年龄的增长降低了 CI 使用者对带口音的说话者的表现，但对视觉线索的获取提高了表现，并且可以部分克服年龄相关的语音理解缺陷，对年龄较大的 CI 使用者尤其如此。
