Helfer Karen S, Freyman Richard L
Department of Communication Disorders, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Ear Hear. 2008 Jan;29(1):87-98. doi: 10.1097/AUD.0b013e31815d638b.
A common complaint of many older adults is difficulty communicating in situations where they must focus on one talker in the presence of other people speaking. In listening environments containing multiple talkers, age-related changes may be caused by increased sensitivity to energetic masking, increased susceptibility to informational masking (e.g., confusion between the target voice and masking voices), and/or cognitive deficits. The purpose of the present study was to tease out these contributions to the difficulties that older adults experience in speech-on-speech masking situations.
Groups of younger, normal-hearing individuals and older adults with varying degrees of hearing sensitivity (n = 12 per group) participated in a study of sentence recognition in the presence of four types of maskers: a two-talker masker consisting of voices of the same sex as the target voice, a two-talker masker of voices of the opposite sex as the target, a signal-envelope-modulated noise derived from the two-talker complex, and a speech-shaped steady noise. Subjects also completed a voice discrimination task to determine the extent to which they were able to incidentally learn to tell apart the target voice from the same-sex masking voices and to examine whether this ability influenced speech-on-speech masking.
Results showed that older adults had significantly poorer performance in the presence of all four types of maskers, with the largest absolute difference for the same-sex masking condition. When the data were analyzed in terms of relative group differences (i.e., adjusting for absolute performance) the greatest effect was found for the opposite-sex masker. Degree of hearing loss was significantly related to performance in several listening conditions. Some older subjects demonstrated a reduced ability to discriminate between the masking and target voices; performance on this task was not related to speech recognition ability.
The overall pattern of results suggests that although amount of informational masking does not seem to differ between older and younger listeners, older adults (particularly those with hearing loss) evidence a deficit in the ability to selectively attend to a target voice, even when the masking voices are from talkers of the opposite sex. Possible explanations for these findings include problems understanding speech in the presence of a masker with temporal and spectral fluctuations and/or age-related changes in cognitive function.
许多老年人常见的一个抱怨是，在必须专注于一个说话者而周围还有其他人讲话的情况下，他们难以进行交流。在包含多个说话者的聆听环境中，与年龄相关的变化可能是由于对能量掩蔽的敏感性增加、对信息掩蔽的易感性增加（例如，目标语音与掩蔽语音之间的混淆）和/或认知缺陷所致。本研究的目的是梳理出这些因素对老年人在语音对语音掩蔽情况下所经历困难的影响。
听力正常的年轻人群体和听力敏感度不同的老年人群体（每组12人）参与了一项句子识别研究，该研究中有四种类型的掩蔽音：一种由与目标语音同性别的声音组成的双说话者掩蔽音、一种由与目标语音异性的声音组成的双说话者掩蔽音、一种从双说话者复合体派生的信号包络调制噪声，以及一种言语频谱稳态噪声。受试者还完成了一项语音辨别任务，以确定他们在多大程度上能够偶然学会区分目标语音和同性掩蔽语音，并检查这种能力是否会影响语音对语音掩蔽。
结果表明，在所有四种类型的掩蔽音存在的情况下，老年人的表现明显较差，在同性掩蔽条件下绝对差异最大。当根据相对组差异（即调整绝对表现）分析数据时，发现异性掩蔽音的影响最大。听力损失程度与几种聆听条件下的表现显著相关。一些老年受试者辨别掩蔽语音和目标语音的能力有所下降；这项任务的表现与语音识别能力无关。
总体结果模式表明，尽管老年人和年轻人在信息掩蔽量方面似乎没有差异，但老年人（尤其是那些有听力损失的人）表现出在选择性关注目标语音方面存在缺陷，即使掩蔽语音来自异性说话者。这些发现的可能解释包括在存在具有时间和频谱波动的掩蔽音时理解语音的问题和/或与年龄相关的认知功能变化。
