Summers Van, Molis Michelle R, Müsch Hannes, Walden Brian E, Surr Rauna K, Cord Mary T
Army Audiology and Speech Center, Walter Reed Army Medical Center, Washington, DC 20307-5001, USA.
Ear Hear. 2003 Apr;24(2):133-42. doi: 10.1097/01.AUD.0000058148.27540.D9.
Recent studies indicate that high-frequency amplification may provide little benefit for listeners with moderate-to-severe high-frequency hearing loss, and may even reduce speech recognition. Moore and colleagues have proposed a direct link between this lack of benefit and the presence of regions of nonfunctioning inner hair cells (dead regions) in the basal cochlea and have suggested that psychophysical tuning curves (PTCs) and tone detection thresholds in threshold-equalizing noise (TEN) are psychoacoustic measures that allow detection of dead regions ([Moore, Huss, Vickers, Glasberg, & Alcántara, 2000]; [Vickers, Moore, & Baer, 2001]). The experiments reported here examine the consistency of TEN and PTC tasks in identifying dead regions in listeners with high-frequency hearing loss.
Seventeen listeners (18 ears) with steeply sloping moderate-to-severe high-frequency hearing loss were tested in PTC and TEN tasks intended to identify ears with high-frequency dead regions. In the PTC task, pure-tone signals of fixed level were masked by narrowband noise that slowly increased in center frequency. For a range of signal frequencies, noise levels at masked threshold were determined as a function of masker frequency. In the TEN task, masked thresholds for pure-tone signals were determined for a fixed-level, 70 dB/ERB TEN masker (for some listeners, 85 or 90 dB/ERB TEN was also tested at selected probe frequencies).
TEN and PTC results agreed on the presence or absence of dead regions at all tested frequencies in 10 of 18 cases (approximately 56% agreement rate). Six ears showed results consistent with either mid- or high-frequency dead regions in both tasks, and four ears did not show evidence of dead regions in either task. In eight ears, the TEN and PTC tasks produced conflicting results at one or more frequencies. In instances where the TEN and PTC results disagreed, the TEN results suggested the presence of dead regions whereas the PTC results did not.
The 56% agreement rate between the TEN and PTC tasks indicates that at least one of these tasks was only partially reliable as a diagnostic tool. Factors unrelated to the presence of dead regions may contribute to excess masking in TEN without producing tip shifts in PTCs. Thus it may be appropriate to view tuning curve results as more reliable in cases where TEN and PTC results disagree. The current results do not provide support for the TEN task as a reliable diagnostic tool for identification of dead regions.
近期研究表明，高频放大对于中重度高频听力损失的聆听者可能益处不大，甚至可能降低言语识别能力。摩尔及其同事提出，这种缺乏益处的情况与基底耳蜗中无功能的内毛细胞区域（死区）的存在存在直接联系，并指出心理声学调谐曲线（PTC）和在阈限均衡噪声（TEN）中的纯音检测阈值是能够检测死区的心理声学指标（[摩尔、胡斯、维克斯、格拉斯伯格和阿尔坎塔拉，2000年]；[维克斯、摩尔和贝尔，2001年]）。本文报告的实验研究了TEN和PTC任务在识别高频听力损失聆听者死区方面的一致性。
对17名（18耳）患有陡峭斜坡型中重度高频听力损失的聆听者进行了PTC和TEN任务测试，旨在识别存在高频死区的耳朵。在PTC任务中，固定强度的纯音信号由中心频率缓慢增加的窄带噪声掩蔽。对于一系列信号频率，根据掩蔽声频率确定掩蔽阈处的噪声水平。在TEN任务中，针对固定强度、70 dB/ERB的TEN掩蔽声确定纯音信号的掩蔽阈（对于部分聆听者，还在选定的探测频率下测试了85或90 dB/ERB的TEN）。
在18例中的10例（一致率约为56%）中，TEN和PTC结果在所有测试频率上关于死区的存在与否达成一致。6只耳朵在两项任务中的结果均与中高频死区一致，4只耳朵在两项任务中均未显示死区迹象。8只耳朵中，TEN和PTC任务在一个或多个频率上产生了相互矛盾的结果。在TEN和PTC结果不一致的情况下，TEN结果表明存在死区，而PTC结果则未表明。
TEN和PTC任务之间56%的一致率表明，这些任务中至少有一项作为诊断工具仅部分可靠。与死区存在无关的因素可能导致TEN中过度掩蔽，而不会在PTC中产生尖峰偏移。因此，在TEN和PTC结果不一致的情况下，将调谐曲线结果视为更可靠可能是合适的。目前的结果不支持将TEN任务作为识别死区的可靠诊断工具。
