Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131, USA.
J Acoust Soc Am. 2011 Feb;129(2):779-91. doi: 10.1121/1.3531796.
An insert ear-canal probe including sound source and microphone can deliver a calibrated sound power level to the ear. The aural power absorbed is proportional to the product of mean-squared forward pressure, ear-canal area, and absorbance, in which the sound field is represented using forward (reverse) waves traveling toward (away from) the eardrum. Forward pressure is composed of incident pressure and its multiple internal reflections between eardrum and probe. Based on a database of measurements in normal-hearing adults from 0.22 to 8 kHz, the transfer-function level of forward relative to incident pressure is boosted below 0.7 kHz and within 4 dB above. The level of forward relative to total pressure is maximal close to 4 kHz with wide variability across ears. A spectrally flat incident-pressure level across frequency produces a nearly flat absorbed power level, in contrast to 19 dB changes in pressure level. Calibrating an ear-canal sound source based on absorbed power may be useful in audiological and research applications. Specifying the tip-to-tail level difference of the suppression tuning curve of stimulus frequency otoacoustic emissions in terms of absorbed power reveals increased cochlear gain at 8 kHz relative to the level difference measured using total pressure.
一种插入耳道的探头，包括声源和麦克风，可以将校准的声功率水平传输到耳朵。吸收的声能与均方根正向压力、耳道面积和吸收率的乘积成正比，其中声场由朝向鼓膜的正向（反向）波表示。正向压力由入射压力及其在鼓膜和探头之间的多次内部反射组成。基于正常听力成年人从 0.22 到 8 kHz 的测量数据库，与入射压力相比，正向传递函数的水平在 0.7 kHz 以下提升了 4 dB。与总压力相比，正向压力的水平在接近 4 kHz 时达到最大值，并且在各个耳朵之间具有很大的可变性。在整个频率上产生平坦的入射压力水平会产生几乎平坦的吸收功率水平，而压力水平的变化为 19 dB。基于吸收功率校准耳道声源可能在听力和研究应用中有用。以吸收功率表示刺激频率耳声发射的抑制调谐曲线的尖端到尾端的水平差，揭示了相对于使用总压力测量的水平差，8 kHz 处耳蜗增益增加。
