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: 2.84). 11/1988; 9(5):243-7. DOI: 10.1097/00003446-198810000-00003
Source: PubMed


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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    • "First, some variation might be expected due to measurement error. Specifically , a number of authors have shown that repeated real ear gain measures using probe microphone equipment can reveal standard deviations in the 1500–3000 Hz frequency range of between approximately 0.5 and 3 dB, depending on the measurement method (e.g., Ringdahl and Leijon, 1984; Dillon and Murray, 1987; Killion and Revit, 1987; Barlow et al, 1988). Standard deviations of less than 1 dB are generally reported when the loudspeaker is placed at a 45u azimuth (e.g., Killion and Revit, 1987) as compared to 0u azimuth. "
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    ABSTRACT: New and improved methods of feedback suppression are routinely introduced in hearing aids; however, comparisons of additional gain before feedback (AGBF) values across instruments are complicated by potential variability across subjects and measurement methods. To examine the variability in AGBF values across individual listeners and an acoustic manikin. A descriptive study of the reliability and variability of the AGBF measured within six commercially available feedback suppression (FS) algorithms using probe microphone techniques. Sixteen participants and an acoustic manikin. The range of AGBF across the six FS algorithms was 0 to 15 dB, consistent with other recent studies. However, measures made in the participants ears and on the acoustic manikin within the same instrument suggest that across instrument comparisons of AGBF measured using acoustic manikin techniques may be misleading, especially when differences between hearing aids are small (i.e., less than 6 dB). Individual subject results also revealed considerable variability within the same FS algorithms. The range of AGBF values was as small as 7 dB and as large as 16 dB depending on the specific FS algorithm, suggesting that some models are much more robust than others. These results suggest caution when selecting FS algorithms clinically since different models can demonstrate similar AGBF when averaging across ears, but result in quite different AGBF values in a single individual ear.
    Journal of the American Academy of Audiology 11/2008; 19(10):748-57. DOI:10.3766/jaaa.19.10.3 · 1.58 Impact Factor
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    • "Unfortunately, a measure of ear canal volume is not a good predictor of the difference in SPL between the real ear and the coupler (Nelson Barlow et al., 1988; Feigin et al., 1989). It was suggested that factors such as impedance of the middle ear and ear canal length may interact with volume to affect ear canal SPL (Nelson Barlow et al., 1988). As such, clinical procedures have since been developed to exploit the RECD measurement so that the individual ear canal acoustics of young patients could be captured and applied in the assessment stage of the hearing instrument fitting process. "
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    ABSTRACT: A discussion of the protocols used particularly in the clinical application of the Desired Sensation Level (DSL) Method is presented in this chapter. In the first section, the measurement and application of acoustic transforms is described in terms of their importance in the assessment phase of the amplification fitting process. Specifically, the implications of individual ear canal acoustics and their impact on accurately defining hearing thresholds are discussed. Detailed information about the statistical strength of the real-ear-to-coupler difference (RECD) measurement and how to obtain the measure in young infants is also provided. In addition, the findings of a study that examined the relationship between behavioral and electrophysiologic thresholds in real-ear SPL is described. The second section presents information related to the electroacoustic verification of hearing instruments. The RECD is discussed in relation to its application in simulated measurements of real-ear hearing instrument performance. In particular, the effects of the transducer and coupling method during the RECD measurement are described in terms of their impact on verification measures. The topics of insertion gain, test signals, and venting are also considered. The third section presents three summary tables that outline the hearing instrument fitting process for infants, children, and adults. Overall, this chapter provides both clinical and scientific information about procedures used in the assessment and verification stages of the DSL Method.
    Trends in Amplification 02/2005; 9(4):199-226. · 1.92 Impact Factor
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