Probe-tube microphone measures in hearing-impaired children and adults.

Boys Town National Institute for Communication Disorders in Children, Omaha, Nebraska.
Ear and Hearing (Impact Factor: 3.26). 11/1988; 9(5):243-7. DOI: 10.1097/00003446-198810000-00003
Source: PubMed

ABSTRACT This study was designed to investigate the reliability of real-ear measurements of sound pressure level (SPL) and to compare these values with two coupler measures of SPL. A commercially available probe tube microphone system was used to measure real ear SPL in both children and adults. Test-retest reliability decreased as a function of frequency for both groups and, in general, was slightly poorer for the children. For both groups, coupler to real ear differences were larger for the 2 cm3 coupler than for the reduced volume coupler; however, no significant differences were observed between groups. In addition, a measure of ear canal volume was not found to be a good predictor of coupler to real ear discrepancies.

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    ABSTRACT: PURPOSE: to evaluate the repeated measurements of the real ear unaided response (REUR), real ear aided response (REAR) and insertion gain (REIG) conducted as face to face (F) and via telecounselling (T). METHOD: longitudinal prospective study. Four measures of REUR, REAR and REIG (carried out with speech noise stimulus presented at 65 dB SPL at 0° azimuth) were obtained in 19 ears in normal hearing adults, face to face and via synchronous telecounsellings with remote control of the real ear equipment and interactive video. Polycom PVX software was used for desktop sharing and video and audio transmission. The Loca Area Network (LAN) USP was used for the connection (transmission rate: 384 kbps). Dahlberg’s casual errors were calculated for obtaining the measures for frequencies from 250 to 8000 Hz. RESULTS: casual errors between F and T measures were very similar, being greater for frequencies above 4 kHz. The differences between F and T measures were no greater than the variability reported for real ear measures. CONCLUSION: probe microphone measures obtained via telecounselling provides reliable results and similar to those obtained by standard procedures.
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    ABSTRACT: 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.
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