Schmiedt R A
J Acoust Soc Am. 1986 May;79(5):1481-90. doi: 10.1121/1.393675.
Acoustic emissions in the form of cubic difference tones (CDT's), 2f1-f2, were measured in the ear canals of gerbils and cats. The state of the cochlea was manipulated by means of acute exposure to noise and was monitored with the aid of the whole-nerve response to tone pips. The resulting shifts in the levels of emissions generated by pairs of primary tones of equal intensity were then compared to the corresponding threshold shifts of the whole-nerve response across frequency. Data obtained from normal ears before injury indicate that the absolute thresholds of the whole-nerve responses across frequency are not necessarily good predictors of the absolute levels of CDT emissions generated by 70- and 80-dB SPL primaries. While high emission levels were often linked to low whole-nerve thresholds in pre-exposed ears, instances of animals with sensitive whole-nerve thresholds coupled with very weak emissions were also found. Conversely, animals with poor whole-nerve thresholds (shifted by up to 30 dB) could occasionally have high levels of emissions. After acute noise injury, however, the shifts of emission levels as a function of the center frequency of the primary-tone pair largely corresponded to the threshold shifts seen in the whole-nerve response. In other words, the temporary level shift of an acoustic emission largely reflected the acute change to a specific cochlear region associated with the primary frequencies.
在沙鼠和猫的耳道中测量了立方差音（CDT，即2f1 - f2）形式的声发射。通过急性噪声暴露来控制耳蜗的状态，并借助对短纯音的全神经反应进行监测。然后将由强度相等的一对初级音调产生的发射水平的变化，与全神经反应在不同频率下相应的阈值变化进行比较。从受伤前的正常耳朵获得的数据表明，全神经反应在不同频率下的绝对阈值不一定能很好地预测由70和80分贝声压级初级音调产生的CDT发射的绝对水平。虽然在预先暴露的耳朵中，高发射水平通常与低全神经阈值相关，但也发现了全神经阈值敏感但发射非常微弱的动物实例。相反，全神经阈值较差（最多偏移30分贝）的动物偶尔也可能有高发射水平。然而，急性噪声损伤后，发射水平随初级音调对中心频率的变化在很大程度上与全神经反应中看到的阈值变化相对应。换句话说，声发射的暂时水平变化在很大程度上反映了与初级频率相关的特定耳蜗区域的急性变化。
