Kummer P, Janssen T, Hulin P, Arnold W
Hals-Nasen-Ohren Klinik, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675, Munich, Germany.
Hear Res. 2000 Aug;146(1-2):47-56. doi: 10.1016/s0378-5955(00)00097-6.
Previous studies described a systematic asymmetry of the level of the 2f(1)-f(2) distortion product otoacoustic emission (DP) in the space of the primary tones levels L(1) and L(2) in normal-hearing humans. Optimal primary tone level separations L(1)-L(2), which result in maximum DP levels, were close to L(1)=L(2) at high levels, but continuously increased with decreasing stimulus level towards L(1)>L(2) (Gaskill and Brown, 1990, J. Acoust. Soc. Am. 88, 821-839). At these optimal L(1)-L(2), however, not only DP levels in normal hearing were maximal, but also trauma-induced DP reductions. A linear equation that approximates optimal L(1)-L(2) level separations thus was suggested to be optimum for use in clinical applications (Whitehead et al., 1995, J. Acoust. Soc. Am. 97, 2359-2377). It was the aim of this study to extend the generality of optimal L(1)-L(2) separations to the typical human test frequency range for f(2) frequencies between 1 and 8 kHz. DPs were measured in 22 normal-hearing human ears at 61 primary tone level combinations, with L(2) between 5 and 65 dB SPL and L(1) between 30 and 70 dB SPL (f(2)/f(1)=1.2). It was found that the systematic dependence of the maximum DP level on the L(1)-L(2) separation is independent on frequency. Optimal L(1)-L(2) level separations may well be approximated by a linear equation L(1)=a L(2)+(1-a) b (after Whitehead et al., 1995) with parameters a=0.4 and b=70 dB SPL at f(2) frequencies between 1 and 8 kHz and L(2) levels between 20 and 65 dB SPL. Below L(2)=20 dB SPL, the optimal L(1) was found to be almost constant. Following previous notions (Gaskill and Brown, 1990), an analysis of basilar membrane response data in experimental animals (after Ruggero and Rich, 1991, Hear. Res. 51, 215-230) is further presented that relates optimal L(1)-L(2) separations to frequency-selective compression of the basilar membrane. Based on the assumption that optimal conditions for the DP generation are equal primary tone responses at the f(2) place, a linear increase of the optimal L(1)-L(2) level separation is graphically demonstrated, similar to our results in human ears.
先前的研究描述了在听力正常的人类中，2f(1)-f(2)畸变产物耳声发射（DP）水平在初级音调水平L(1)和L(2)空间中的系统不对称性。在高声级时，导致最大DP水平的最佳初级音调水平间隔L(1)-L(2)接近L(1)=L(2)，但随着刺激水平降低，L(1)-L(2)持续增加，趋向于L(1)>L(2)（Gaskill和Brown，1990年，《美国声学学会杂志》88卷，821 - 839页）。然而，在这些最佳L(1)-L(2)时，不仅正常听力中的DP水平最大，而且创伤引起的DP降低也最大。因此，有人提出一个近似最佳L(1)-L(2)水平间隔的线性方程在临床应用中是最佳的（Whitehead等人，1995年，《美国声学学会杂志》97卷，2359 - 2377页）。本研究的目的是将最佳L(1)-L(2)间隔的普遍性扩展到f(2)频率在1至8 kHz之间的典型人类测试频率范围。在22只听力正常的人耳中，以61种初级音调水平组合测量DP，L(2)在5至65 dB SPL之间，L(1)在30至70 dB SPL之间（f(2)/f(1)=1.2）。研究发现，最大DP水平对L(1)-L(2)间隔的系统依赖性与频率无关。最佳L(1)-L(2)水平间隔可以很好地用线性方程L(1)=a L(2)+(1 - a) b（参照Whitehead等人，1995年）近似，在f(2)频率为1至8 kHz且L(2)水平为20至65 dB SPL时，参数a = 0.4，b = 70 dB SPL。在L(2)=20 dB SPL以下，发现最佳L(1)几乎恒定。根据先前的观点（Gaskill和Brown，1990年），进一步呈现了对实验动物基底膜反应数据的分析（参照Ruggero和Rich，1991年，《听觉研究》51卷，215 - 230页），该分析将最佳L(1)-L(2)间隔与基底膜的频率选择性压缩联系起来。基于DP产生的最佳条件是在f(2)位置处初级音调反应相等的假设，以图形方式展示了最佳L(1)-L(2)水平间隔的线性增加，类似于我们在人耳中的结果。
