Department of Communication Disorders, University of Massachusetts, Amherst, MA 01003, USA.
J Acoust Soc Am. 2009 Nov;126(5):2556-69. doi: 10.1121/1.3216912.
Two experiments examined the effects of source-to-listener distance (SLD) on sentence recognition in simulations of cochlear implant usage in noisy, reverberant rooms. Experiment 1 tested sentence recognition for three locations in the reverberant field of a small classroom (volume=79.2 m(3)). Subjects listened to sentences mixed with speech-spectrum noise that were processed with simulated reverberation followed by either vocoding (6, 12, or 24 spectral channels) or no further processing. Results indicated that changes in SLD within a small room produced only minor changes in recognition performance, a finding likely related to the listener remaining in the reverberant field. Experiment 2 tested sentence recognition for a simulated six-channel implant in a larger classroom (volume=175.9 m(3)) with varying levels of reverberation that could place the three listening locations in either the direct or reverberant field of the room. Results indicated that reducing SLD did improve performance, particularly when direct sound dominated the signal, but did not completely eliminate the effects of reverberation. Scores for both experiments were predicted accurately from speech transmission index values that modeled the effects of SLD, reverberation, and noise in terms of their effects on modulations of the speech envelope. Such models may prove to be a useful predictive tool for evaluating the quality of listening environments for cochlear implant users.
两项实验研究了在模拟使用人工耳蜗的噪声、混响房间中，声源到听者距离（SLD）对句子识别的影响。实验 1 在一个小教室的混响场中测试了三个位置的句子识别（体积=79.2 m³）。受试者听了用模拟混响处理的句子，这些句子与语音频谱噪声混合，然后进行语音编码（6、12 或 24 个频谱通道）或不进行进一步处理。结果表明，在小房间内改变 SLD 只会导致识别性能的微小变化，这一发现可能与听者仍处于混响场有关。实验 2 在一个更大的教室（体积=175.9 m³）中模拟了一个六通道的植入物，在不同程度的混响下，三个听力位置可以在房间的直达声或混响声场中。结果表明，降低 SLD 确实可以提高性能，尤其是在直达声占主导地位时，但不能完全消除混响的影响。两个实验的得分都可以通过语音传输指数值准确预测，该指数值根据 SLD、混响和噪声对语音包络调制的影响来模拟它们的影响。这种模型可能成为评估人工耳蜗使用者听力环境质量的有用预测工具。
