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: 2.83). 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: Audiometric measurements are traditionally made in dB HL, which by definition are specified relative to the sound pressure level (SPL) in a coupler. Real-ear dB SPL is then estimated by applying an average ear transform to the coupler value. However, individual variation in ear canal acoustics and variations in transducer placement strongly influence the dB SPL of signals arriving at the eardrum. In this paper, data from 1814 ears are presented, showing that the distribution of eardrum dB SPL for a fixed signal level varies across ears and across frequency by as much as 40 dB. The impact of this variance upon hearing aid targets computed with the NAL-NL1 fitting algorithm is examined by comparing the targets obtained from using an average transform with those obtained when audiometric data in dB SPL are obtained by applying individually measured real-ear-to-coupler difference (RECD) values to dB HL thresholds. The impact can be considerable. Sumario Tradicionalmente, las mediciones audiométricas se realizan en dB HL, que por definitión se especifican en relación con el nivel de presíón sonora (SPL) en un acoplador. Los dB SPL de oído-real se estiman, aplicando una transformatión promedio al oído, en relación con el valor del acoplador. Sin embargo, las variaciones individuales en la acústica del conducto auditivo y las variaciones en la colocación del transductor influyen fuertemente en las señales en dB SPL, que llegan a la membrana timpánica. En este artículo, se presenta la información de 1814 oídos, mostrando que la distribución de los dB SPL en el tímpano, para un nível fijo de señal, varía en los diferentes oídos y en las diferentes frecuencias hasta en 40 dB. Se examinó el impacto de esta variación sobre las metas en los auxiliares auditivos, estimadas con el algoritmo de adaptatión NAL-NL 1. Este análisis se realizó comparando los valores meta logrados utilizando una transformación promedio, con aquellos datos audiométricos en dB SPL, obtenidos aplicando individualmente las mediciones de la diferencia oído real/acoplador (RECD) a los umbrales en dB HL. El impacto puede ser considerable.
    International Journal of Audiology 07/2009; 42(6). DOI:10.3109/14992020309101324 · 1.43 Impact Factor