Auditory Physiology Laboratory, Department of Speech and Hearing Science, Arizona State University, 3430 Coor Hall, Tempe, Arizona 85287-0102, USA.
J Acoust Soc Am. 2011 Feb;129(2):828-39. doi: 10.1121/1.3531813.
Distortion product otoacoustic emissions (DPOAEs) were measured using sinusoidal amplitude modulation (AM) tones. When one of the primary stimuli (f(1) or f(2), f(1) < f(2)) was amplitude modulated, a series of changes in the cubic difference tone (CDT) were observed. In the frequency domain, multiple sidebands were present around the CDT and their sizes grew with the modulation depth of the AM stimulus. In the time domain, the CDT showed different modulation patterns between two major signal conditions: the AM tone was used as the f(1) or the f(2). The CDT amplitude followed the AM tone when the f(1) was amplitude modulated. However, when the AM tone acted as the f(2), the CDT showed a more complex modulation pattern with a notch present at the AM tone peak. The relatively linear dependence of CDT on f(1) and the nonlinear relation with f(2) can be explained with a variable gain-control model representing hair cell functions at the DPOAE generation site. It is likely that processing of AM signals at a particular cochlear location depends on whether the hair cells are tuned to the frequency of the carrier. Nonlinear modulation is related to on-frequency carriers and off-frequency carriers are processed relatively linearly.
畸变产物耳声发射（DPOAEs）是使用正弦幅度调制（AM）音进行测量的。当一个初级刺激（f(1)或 f(2)，f(1) < f(2)）被幅度调制时，观察到三次差频（CDT）的一系列变化。在频域中，在 CDT 周围存在多个边带，并且它们的大小随 AM 刺激的调制深度而增加。在时域中，CDT 在两种主要信号条件之间表现出不同的调制模式：AM 音用作 f(1)或 f(2)。当 f(1)被幅度调制时，CDT 幅度跟随 AM 音。然而，当 AM 音作为 f(2)时，CDT 显示出更复杂的调制模式，在 AM 音峰值处存在一个缺口。CDT 与 f(1)的相对线性关系和与 f(2)的非线性关系可以用代表 DPOAE 产生部位毛细胞功能的可变增益控制模型来解释。在特定耳蜗位置处理 AM 信号的方式可能取决于毛细胞是否调谐到载波的频率。非线性调制与载波频率有关，而离频载波则以相对线性的方式进行处理。
