Department of Communication Sciences and Disorders, University of Iowa, Iowa City, Iowa 52242, USA.
J Acoust Soc Am. 2011 Dec;130(6):3882-92. doi: 10.1121/1.3655878.
Quantifying ear-canal sound level in forward pressure has been suggested as a more accurate and practical alternative to sound pressure level (SPL) calibrations used in clinical settings. The mathematical isolation of forward (and reverse) pressure requires defining the Thévenin-equivalent impedance and pressure of the sound source and characteristic impedance of the load; however, the extent to which inaccuracies in characterizing the source and/or load impact forward pressure level (FPL) calibrations has not been specifically evaluated. This study examined how commercially available probe tips and estimates of characteristic impedance impact the calculation of forward and reverse pressure in a number of test cavities with dimensions chosen to reflect human ear-canal dimensions. Results demonstrate that FPL calibration, which has already been shown to be more accurate than in situ SPL calibration, can be improved particularly around standing-wave null frequencies by refining estimates of characteristic impedance. Better estimates allow FPL to be accurately calculated at least through 10 kHz using a variety of probe tips in test cavities of different sizes, suggesting that FPL calibration can be performed in ear canals of all sizes. Additionally, FPL calibration appears a reasonable option when quantifying the levels of extended high-frequency (10-18 kHz) stimuli.
已经有人提出，在临床环境中，量化耳道中的正向声压级比使用声压级（SPL）校准更为准确和实用。正向（和反向）压力的数学隔离需要定义声源的 Thévenin 等效阻抗和压力以及负载的特性阻抗；然而，尚未具体评估声源和/或负载特性的不准确性对正向压力级（FPL）校准的影响程度。本研究检查了在尺寸选择以反映人耳道尺寸的多个测试腔中，商业上可用的探头尖端和特性阻抗的估计值如何影响正向和反向压力的计算。结果表明，FPL 校准已经被证明比原位 SPL 校准更准确，通过改进特性阻抗的估计值，特别是在驻波零频率附近，可以进一步提高校准的准确性。更好的估计值允许使用各种探头尖端在不同尺寸的测试腔中至少在 10 kHz 处准确计算 FPL，这表明 FPL 校准可以在所有尺寸的耳道中进行。此外，当量化扩展高频（10-18 kHz）刺激的水平时，FPL 校准似乎是一个合理的选择。
