Clin Exp Otorhinolaryngol.  2020 Feb;13(1):29-35. 10.21053/ceo.2019.00577.

Development of Sound Field Audiometry System for Small Audiometric Booths and Comparison of Its Equivalence With Traditional System

• Jung EK
• Choi YM
• Kim EJ
• Lee S
• Cho HH

• KMID: 2501294
• DOI: http://doi.org/10.21053/ceo.2019.00577

Abstract

Objectives
. Sound field (SF) audiometry tests are usually conducted in audiometric booths measuring greater than 2×2 m in size. However, most private ENT clinics carry about 1×1-m-sized audiometric booths, making SF audiometry testing difficult to perform. The aims of this study were to develop an SF audiometry system for use in smaller audiometric booths and compare its performance with traditional system.
Methods
. The newly developed SF audiometry system can yield an SF signal at a distance of about 30 cm from the subject’s ears. Its height can be adjusted according to the subject’s head height. We compared SF hearing results between the new SF system and the traditional SF audiometry system in 20 adults with normal hearing (40 ears) and 24 adults with impaired hearing levels (38 ears) who wore hearing aids. Comparative parameters included warble tone audiometry threshold, a speech reception threshold (SRT), and a speech discrimination score (SDS). For statistical analysis, paired t-test was used. The equivalence of both SF systems was tested using two one-sided test (TOST) with a margin of 5 dB (normal hearing participants) and 10 dB (hearing aids wearing participants).
Results
. Among participants with normal hearing, warble tone hearing thresholds of 0.5, 1, 2, and 4 kHz, average values of these four frequencies, and SRT were similar between the two systems (all P>0.05). Participants with hearing aids showed similar warble tone threshold and SRT (P>0.05) in both systems except for threshold of 4 kHz (P=0.033). SDS was significantly higher in the newly developed system (P<0.05). TOST results showed equivalent SF audiometry results using either system.
Conclusion
. Audiometric results of the newly developed SF audiometry system were equivalent to those of a traditional system. Therefore, the small SF audiometry system can be used at small audiometric booths present in most private ENT clinics.

Keyword

Hearing Aid; Audiometry; Sound; Hearing Loss

Figure

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  Fig. 1. Traditional sound field audiometry system installed in a large sized audiometric booth.

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  Fig. 2. Changes in head size with age. (A) Head size measurement using temporal bone computed tomography. (B) Changes in interaural length (IAL) with age. (C) Changes in occipito-aural length (OAL) with age.

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  Fig. 3. Newly developed sound field audiometry system for small audiometric booths. (A) Schematic. (B) Newly developed sound field audiometry system installed in a small audiometric booth.

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  Fig. 4. Comparison of sound field (SF) warble tone audiometry results of participants with normal hearing under traditional and newly developed SF systems. (A) Comparative hearing thresholds in both SF systems. No significant difference was detected at 0.5, 1, 2, 4 kHz, or average warble tone hearing threshold (paired t-test). Average refers to six-frequency average hearing thresholds [(0.5 kHz+2×1 kHz+2×2 kHz+4 kHz)/6]. (B) Results of two one-sided test (TOST) showing equivalent SF audiometry results under the two systems within 90% confidence intervals (CIs) at a margin of 5 dB for each frequency. Error bar: standard deviation.

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  Fig. 5. Comparison of sound field (SF)-aided warble tone audiometry results among patients wearing hearing aids under traditional and newly developed SF systems. (A) Comparative hearing thresholds in both SF systems. No significant difference was found at 0.5, 1, 2 kHz, or average warble tone threshold, or speech reception test thresholds (paired t-test). (B) Results of two one-sided test (TOST) showing equivalent SF aided audiometry results under the two systems within 90% confidence intervals (CIs) at a margin of 10 dB for each frequency. (C) Measures of speech discrimination score (SDS) at 65 dB HL and maximum comfort level (MCL) under both SF systems. The SDS of the newly developed SF system was higher than that of the traditional SF system (P<0.05, paired t-test). Error bar: standard deviation. SDT, speech discrimination test.

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