Comparison of in-situ calibration methods for quantifying input to the middle ear.
Sound pressure level in-situ measurements are sensitive to standing-wave pressure minima and have the potential to result in over-amplification with risk to residual hearing in hearing-aid fittings. Forward pressure level (FPL) quantifies the pressure traveling toward the tympanic membrane and may be a potential solution as it is insensitive to ear-canal pressure minima. Derivation of FPL is dependent on a Thevenin-equivalent source calibration technique yielding source pressure and impedance. This technique is found to accurately decompose cavity pressure into incident and reflected components in both a hard-walled test cavity and in the human ear canal through the derivation of a second sound-level measure termed integrated pressure level (IPL). IPL is quantified by the sum of incident and reflected pressure amplitudes. FPL and IPL were both investigated as measures of sound-level entering the middle ear. FPL may be a better measure of middle-ear input because IPL is more dependent on middle-ear reflectance and ear-canal conductance. The use of FPL in hearing-aid applications is expected to provide an accurate means of quantifying high-frequency amplification.
Lewis
James D
JD
Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131, USA. james-lewis@uiowa.edu
McCreery
Ryan W
RW
Neely
Stephen T
ST
Stelmachowicz
Patricia G
PG
D000161:Acoustic Stimulation; D000162:Acoustics; D000293:Adolescent; D000465:Algorithms; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold; D002138:Calibration; D002648:Child; D004424:Ear Canal / Q000502:physiology; D004432:Ear, Middle / Q000502:physiology; D004581:Electronics / Q000295:instrumentation / Q000379:methods*; D006309:Hearing / Q000502:physiology; D006801:Humans; D011312:Pressure; D013016:Sound; D055815:Young Adult