MODULATION DETECTION IN SUBJECTS WITH RELATIVELY FLAT HEARING LOSSES
MODULATION DETECTION IN SUBJECTS WITH RELATIVELY FLAT HEARING LOSSES
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DOI：
10.1044/jshr.3503.642
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发表时间：
1992-06-01
期刊：
影响因子：
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通讯作者：
GLEITMAN, RM
中科院分区：
文献类型：
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作者：
BACON, SP;GLEITMAN, RM
在5名听力正常的受试者和8名相对平缓、轻度至中度听力损失的受试者中，测量了调制检测阈值作为调制频率的函数。载波是一种宽带噪声，在两个观测区间中的一个进行正弦调幅（SAM）。载波的频谱电平范围从- 10到50 dB SPL，并且，对于给定的载波电平，调制频率从2到1024hz变化。时间调制传递函数（TMTFs）与描述低通滤波器函数的简单方程拟合得很好。正常听力受试者的TMTFs相对独立于载波电平，但推导出的时间常数有随载波电平降低而略有增加的趋势，从30 dB声压级时的平均值2.5 msec增加到- 10 dB声压级时的平均值6.0 msec。此外，当载波的压力谱电平从0降至- 10 dB SPL时，对调幅（AM）的灵敏度降低了约4 dB。8名听障者中有7名的时间常数与正常听障者相近，但听障者的时间常数略大。然而，当在可比感觉水平（SLs）下进行比较时，两组受试者的TMTFs在数量上是相似的，除了在最低的SL （20 dB）下，听力受损的受试者通常比正常听力的受试者对AM更敏感，并且从他们的TMTFs中得出的时间常数略小。这些结果与先前发表的结果一起表明，宽的听力带宽对于时间分辨率任务的正常表现很重要。无论在声级相等还是声级相等的情况下进行比较，其中一名听障受试者的时间常数都明显长于正常人，这表明其他因素也可能很重要。
Modulation detection thresholds were measured as a function of modulation frequency in 5 normal-hearing subjects and in 8 subjects with relatively flat, slight-to-moderate hearing losses. The carrier was a broadband noise that was sinusoidally amplitude modulated (SAM) in one of two observation intervals. The spectrum level of the carrier ranged from - 10 to 50 dB SPL, and, for a given carrier level, modulation frequency varied from 2 to 1024 Hz. The temporal modulation transfer functions (TMTFs) were fitted very well with a simple equation describing a low-pass filter function. The TMTFs from the normal-hearing subjects were relatively independent of carrier level, although the derived time constant tended to increase slightly with decreases in carrier level, from an average value of 2.5 msec at 30 dB SPL to 6.0 msec at - 1 0 dB SPL. In addition, sensitivity to amplitude modulation (AM) decreased by about 4 dB as the pressure spectrum level of the carrier was decreased from 0 to - 1 0 dB SPL. The TMTFs f rom 7 of the 8 hearing-impaired subjects were similar to those from the normal-hearing subjects when the carriers were presented at equal SPLs, except that the derived time constants were slightly larger in the subjects with hearing impairment. When comparisons were made at comparable sensation levels (SLs), however, the TMTFs from the two groups of subjects were quantitatively similar, with the exception that at the lowest SL (20 dB), hearing-impaired subjects typically were more sensitive to AM than normal-hearing subjects, and the derived time constants from their TMTFs were somewhat smaller. These results, taken together with previously published results, suggest that a broad listening bandwidth is important for normal performance on a temporal resolution task. That the time constant from one of the hearing-impaired subjects was significantly longer than normal, regardless of whether the comparisons were made at equal SPL or equal SL, indicates that other factors can also be important.