Brochier Tim, McDermott Hugh J, McKay Colette M
Department of Medical Bionics, University of Melbourne, Parkville, Victoria 3010, Australia.
The Bionics Institute, 384-388 Albert Street, East Melbourne, Victoria 3002, Australia.
J Acoust Soc Am. 2017 Jun;141(6):4097. doi: 10.1121/1.4983658.
In order to improve speech understanding for cochlear implant users, it is important to maximize the transmission of temporal information. The combined effects of stimulation rate and presentation level on temporal information transfer and speech understanding remain unclear. The present study systematically varied presentation level (60, 50, and 40 dBA) and stimulation rate [500 and 2400 pulses per second per electrode (pps)] in order to observe how the effect of rate on speech understanding changes for different presentation levels. Speech recognition in quiet and noise, and acoustic amplitude modulation detection thresholds (AMDTs) were measured with acoustic stimuli presented to speech processors via direct audio input (DAI). With the 500 pps processor, results showed significantly better performance for consonant-vowel nucleus-consonant words in quiet, and a reduced effect of noise on sentence recognition. However, no rate or level effect was found for AMDTs, perhaps partly because of amplitude compression in the sound processor. AMDTs were found to be strongly correlated with the effect of noise on sentence perception at low levels. These results indicate that AMDTs, at least when measured with the CP910 Freedom speech processor via DAI, explain between-subject variance of speech understanding, but do not explain within-subject variance for different rates and levels.
为了提高人工耳蜗使用者的言语理解能力，最大化时间信息的传递非常重要。刺激速率和呈现水平对时间信息传递及言语理解的综合影响仍不明确。本研究系统地改变呈现水平（60、50和40分贝声压级）和刺激速率[每个电极每秒500和2400脉冲（pps）]，以观察不同呈现水平下速率对言语理解的影响如何变化。通过直接音频输入（DAI）向言语处理器呈现声学刺激，测量安静和噪声环境下的言语识别以及声幅调制检测阈值（AMDT）。对于每秒500脉冲的处理器，结果显示在安静环境中辅音-元音核-辅音单词的表现明显更好，并且噪声对句子识别的影响减小。然而，未发现AMDT存在速率或水平效应，这可能部分是由于声音处理器中的幅度压缩。发现AMDT与低水平噪声对句子感知的影响密切相关。这些结果表明，至少通过DAI用CP910 Freedom言语处理器测量时，AMDT可以解释言语理解的个体间差异，但不能解释不同速率和水平下的个体内差异。
