Braun Martin
Neuroscience of Music, Gansbyn 14, S-67195 Klässbol, Sweden.
Hear Res. 2006 May;215(1-2):39-46. doi: 10.1016/j.heares.2006.03.008. Epub 2006 Apr 27.
The recording of otoacoustic emissions (OAEs) is today a widely used tool in medical diagnosis. The mechanisms of OAE generation in the cochlea and their transmission to the external ear canal, however, are not well understood and a matter of long-standing debates. Here, the frequency distribution of 1660 spontaneous otoacoustic emissions (SOAEs) from three surveys, covering 296 human subjects, is analyzed. Neonates show a monomodal distribution with a peak at 4 kHz, but both children (5-11 y) and adults show an identical bimodal distribution, with two peaks in an octave distance (1.5 and 3 kHz). For the combined children and adult data, distribution density at the two peak tops is 2.8 and 2.7 times as high as at the low between them. Mean SOAE amplitudes are unrelated to the two peaks, but show a significant narrow-band dip precisely at the low in between at 2140 Hz (P<0.008). External ear canal resonance can explain the single 4 kHz mode at birth and the 3 kHz mode in children and adults. The octave shifted 1.5 kHz mode remains without mechanical explanation. It may reflect descending neural influence from central octave band processing. The results are relevant for the interpretation of OAE levels in medical diagnosis.
耳声发射（OAE）记录如今是医学诊断中广泛使用的工具。然而，耳蜗中OAE产生的机制及其向外耳道的传输尚未得到很好的理解，并且是长期争论的话题。在此，分析了来自三项涵盖296名人类受试者的调查中的1660个自发性耳声发射（SOAE）的频率分布。新生儿呈现单峰分布，峰值在4 kHz处，但儿童（5 - 11岁）和成人都呈现相同的双峰分布，两个峰值相隔一个倍频程（1.5和3 kHz）。对于儿童和成人的综合数据，两个峰值处的分布密度分别是它们之间最低点处的2.8倍和2.7倍。SOAE的平均振幅与这两个峰值无关，但恰好在2140 Hz的最低点处呈现出显著的窄带下降（P < 0.008）。外耳道共振可以解释出生时单一的4 kHz模式以及儿童和成人中的3 kHz模式。相差一个倍频程的1.5 kHz模式仍然没有力学解释。它可能反映了来自中央倍频程带处理的下行神经影响。这些结果对于医学诊断中OAE水平的解释具有重要意义。
