Objective This study compares measurements of ear-canal reflectance (ECR) to other objective measurements of middle-ear function including, audiometry, umbo velocity (VU), and tympanometry in a population of strictly defined normal hearing ears. Design Data were prospectively gathered from 58 ears of 29 normal hearing subjects, 16 female and 13 male, aged 22–64 years. Subjects met all of the following criteria to be considered as having normal hearing. (1) No history of significant middle-ear disease. (2) No history of otologic surgery. (3) Normal tympanic membrane (TM) on otoscopy. (4) Pure-tone audiometric thresholds of 20 dB HL or better for 0.25 – 8 kHz. (5) Air-bone gaps no greater than 15 dB at 0.25 kHz and 10 dB for 0.5 – 4 kHz. (6) Normal, type-A peaked tympanograms. (7) All subjects had two “normal” ears (as defined by these criteria). Measurements included pure-tone audiometry for 0.25 – 8 kHz, standard 226 Hz tympanometry, Ear canal reflectance(ECR) for 0.2 – 6 kHz at 60 dB SPL using the Mimosa Acoustics HearID system, and Umbo Velocity (VU ) for 0.3 – 6 kHz at 70–90 dB SPL using the HLV-1000 laser Doppler vibrometer (Polytec Inc). Results Mean power reflectance (|ECR|2) was near 1.0 at 0.2– 0.3 kHz, decreased to a broad minimum of 0.3 to 0.4 between 1 and 4 kHz, and then sharply increased to almost 0.8 by 6 kHz. The mean pressure reflectance phase angle (∠ECR) plotted on a linear frequency scale showed a group delay of approximately 0.1 ms for 0.2 – 6 kHz. Small significant differences were observed in |ECR|2 at the lowest frequencies between right and left ears, and between males and females at 4 kHz. |ECR|2 decreased with age, but reached significance only at 1 kHz. Our ECR measurements were generally similar to previous published reports. Highly significant negative correlations were found between |ECR|2 and VU for frequencies below 1 kHz. Significant correlations were also found between the tympanometrically determined peak total compliance and |ECR|2 and The results suggest that middle-ear compliance VU at frequencies below 1 kHz. contributes significantly to the measured power reflectance and umbo velocity at frequencies below 1 kHz, but not at higher frequencies. Conclusions This study has established a database of objective measurements of middle ear function (ear-canal reflectance, umbo velocity, tympanometry) in a population of strictly defined normal hearing ears. The data will promote our understanding of normal middle ear function, and will serve as a control for comparison to similar measurements made in pathological ears.

Objective The goal of the present study was to investigate the clinical utility of measurements of ear-canal reflectance (ECR) in a population of patients with conductive hearing loss in the presence of an intact, healthy tympanic membrane (TM) and an aerated middle ear. We also sought to compare the diagnostic accuracy of umbo velocity (VU) measurements and measurements of ECR in the same group of patients. Design This prospective study comprised 31 adult patients with conductive hearing loss, of which 14 had surgically-confirmed stapes fixation due to otosclerosis, 6 had surgically-confirmed ossicular discontinuity, and 11 had CT- and VEMP-confirmed superior semicircular canal dehiscence (SCD). Measurements on all 31 ears included pure-tone audiometry for 0.25 – 8 kHz, ECR for 0.2 – 6 kHz using the Mimosa Acoustics HearID system, and VU for 0.3 – 6 kHz using the HLV-1000 laser Doppler vibrometer (Polytec Inc). We analyzed power reflectance |ECR|2 as well as the absorbance level = 10×log10(1−|ECR|2). All measurements were made prior to any surgical intervention. The VU and ECR data were plotted against normative data obtained in a companion study of 58 strictly defined normal ears (Rosowski et al. 2011). Results Small increases in |ECR|2 at low-to-mid frequencies (400–1000 Hz) were observed in cases with stapes fixation, while narrow-band decreases were seen for both SCD and ossicular discontinuity. The SCD and ossicular discontinuity differed in that the SCD had smaller decreases at mid-frequency (~1000 Hz), while ossicular discontinuity had larger decreases at lower frequencies (500–800 Hz). SCD tended to have less air-bone gap at high frequencies (1–4 kHz) compared to stapes fixation and ossicular discontinuity. The |ECR|2 measurements, in conjunction with audiometry, could successfully separate 28 of the 31 cases into the three pathologies. By comparison, VU measurements, in conjunction with audiometry, could successfully separate various pathologies in 29 of 31 cases. Conclusions The combination of |ECR|2 with audiometry showed clinical utility in the differential diagnosis of conductive hearing loss in the presence of an intact TM and an aerated middle ear, and appears to be of similar sensitivity and specificity to measurements of VU plus audiometry. Additional research is needed to expand upon these promising preliminary results.

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