Waisman Center, University of Wisconsin-Madison, 1500 Highland Avenue, Madison, Wisconsin 53705, USA.
Department of Hearing and Speech Sciences, University of Maryland at College Park, College Park, Maryland 20742, USA.
J Acoust Soc Am. 2019 May;145(5):2982. doi: 10.1121/1.5102158.
For normal-hearing (NH) listeners, interaural information in both temporal envelope and temporal fine structure contribute to binaural unmasking of target signals in background noise; however, in many conditions low-frequency interaural information in temporal fine structure produces greater binaural unmasking. For bilateral cochlear-implant (CI) listeners, interaural information in temporal envelope contributes to binaural unmasking; however, the effect of encoding temporal fine structure information in electrical pulse timing (PT) is not fully understood. In this study, diotic and dichotic signal detection thresholds were measured in CI listeners using bilaterally synchronized single-electrode stimulation for conditions in which the temporal envelope was presented without temporal fine structure encoded (constant-rate pulses) or with temporal fine structure encoded (pulses timed to peaks of the temporal fine structure). CI listeners showed greater binaural unmasking at 125 pps with temporal fine structure encoded than without. There was no significant effect of encoding temporal fine structure at 250 pps. A similar pattern of performance was shown by NH listeners presented with acoustic pulse trains designed to simulate CI stimulation. The results suggest a trade-off across low rates between interaural information obtained from temporal envelope and that obtained from temporal fine structure encoded in PT.
对于正常听力（NH）的听众来说，时间包络和时间精细结构中的双耳信息都有助于在背景噪声中掩蔽目标信号；然而，在许多情况下，低频时间精细结构中的双耳信息会产生更大的双耳掩蔽。对于双侧人工耳蜗（CI）听众来说，时间包络中的双耳信息有助于双耳掩蔽；然而，电脉冲定时（PT）中编码时间精细结构信息的效果尚不完全清楚。在这项研究中，使用双侧同步单电极刺激测量了 CI 听众的双音节和双音节信号检测阈值，其中时间包络在没有编码时间精细结构（恒速脉冲）或具有编码时间精细结构（脉冲定时到时间精细结构的峰值）的情况下呈现。CI 听众在 125pps 时表现出比没有编码时更好的时间精细结构掩蔽。在 250pps 时，编码时间精细结构没有显著影响。用设计来模拟 CI 刺激的声脉冲序列呈现给 NH 听众，也表现出类似的表现模式。结果表明，在低速率下，时间包络中获得的双耳信息与 PT 中编码的时间精细结构中获得的双耳信息之间存在权衡。
