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. 2008 Dec;124(6):3708-19.
doi: 10.1121/1.3001712.

Wideband absorbance tympanometry using pressure sweeps: system development and results on adults with normal hearing

Yi-Wen Liu  1 , Chris A Sanford, John C Ellison, Denis F Fitzpatrick, Michael P Gorga, Douglas H Keefe
Affiliations

Wideband absorbance tympanometry using pressure sweeps: system development and results on adults with normal hearing

Yi-Wen Liu et al. J Acoust Soc Am. 2008 Dec.

Abstract

A system with potential for middle-ear screening and diagnostic testing was developed for the measurement of wideband energy absorbance (EA) in the ear canal as a function of air pressure, and tested on adults with normal hearing. Using a click stimulus, the EA was measured at 60 frequencies between 0.226 and 8 kHz. Ambient-pressure results were similar to past studies. To perform tympanometry, air pressure in the ear canal was controlled automatically to sweep between -300 and 200 daPa (ascending/descending directions) using sweep speeds of approximately 75, 100, 200, and 400 daPas. Thus, the measurement time for wideband tympanometry ranged from 1.5 to 7 s and was suitable for clinical applications. A bandpass tympanogram, calculated for each ear by frequency averaging EA from 0.38 to 2 kHz, had a single-peak shape; however, its tympanometric peak pressure (TPP) shifted as a function of sweep speed and direction. EA estimated at the TPP was similar across different sweep speeds, but was higher below 2 kHz than EA measured at ambient pressure. Future studies of EA on normal ears of a different age group or on impaired ears may be compared with the adult normal baseline obtained in this study.

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Figures

Figure 1
Figure 1
Schematic diagram of instrumentation.
Figure 2
Figure 2
A typical result of probe calibration. (A) The incident sound recorded by A∕D. (B) SPL spectra of the incident wave and the frequency responses in the two calibration tubes.
Figure 3
Figure 3
Pressure sweep and automatic control. The thick line shows air pressure at the time each click occurred. The dashed line was manually added as a reference. The squares showed where click responses were rejected due to acoustical artifacts.
Figure 4
Figure 4
EA measured at ambient pressure, plotted at 60 frequencies spaced 1∕12 octave apart. Solid lines show 10th, 25th, 50th, 75th, and 90th percentiles, respectively, of the normal hearing subjects (N=92 ears).
Figure 5
Figure 5
EA as a function of frequency and air pressure. Sweep speed: −75 daPa∕s. (a), (b), and (c): 10th, 50th, and 90th percentiles, respectively, of adult normative data (N=92 ears).
Figure 6
Figure 6
Minimum EA across subjects (N=92 ears). Empty regions indicate where the minimum EA was found negative.
Figure 7
Figure 7
Examples of single-frequency admittance magnitude tympanograms extracted from wideband tympanometry. Results from randomly selected ears. (A) 226 Hz. (B) 1 kHz.
Figure 8
Figure 8
Frequency-averaged (0.38–2 kHz) EA as a function of air pressure. Each panel shows results at a different sweep speed and direction, and traces show responses from individual ears (N=29 ears).
Figure 9
Figure 9
Peak-pressure difference (PPD) vs pressure-sweep speed. Circles and bars show means and SDs (N=29 ears). Asterisks show minimum and maximum PPD at each speed.
Figure 10
Figure 10
Wideband EA estimated at TPP (pEA). Pressure-sweep speeds are listed in each panel. Solid lines indicate the 10th, 50th, and 90th percentiles, respectively (N=29 ears). For comparison, the shaded area shows the 10th to 90th percentile range that was measured with the sweep speed of −75 daPa∕s.
Figure 11
Figure 11
Comparison of pEA and aEA across frequencies. Sweep speed: −75 daPa∕s. Top: Thick lines show 10th, 50th, and 90th percentiles of pEA, and thin lines show the same percentiles of aEA (N=92 ears). Bottom: Mean and SD of ΔEA.
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