Evaluation of Two Circumaural Earphones for Audiometry

Objective: The Sennheiser HDA 200 earphone, a standard circumaural earphone used in audiometry for many years, is out of production and is replaced by the RadioEar DD450. The Sennheiser HD 280 Pro earphone is a consumer product that has characteristics that may be suitable for audiometry and may be a low-cost alternative to the DD450. The DD450 and HD 280 Pro earphones were compared with the HDA 200 for use in audiometry. Design: RadioEar DD450 and Sennheiser HD 280 Pro earphones were evaluated for reference equivalent threshold sound pressure levels (RETSPLs), ambient-noise attenuation, and occlusion effects. Audiometric thresholds measured on a group of normal-hearing adults were used to determine RETSPLs. Ambient-noise attenuation was determined by measuring the sound pressure in the ear canal produced by a broadband signal from a loudspeaker with and without occlusion by the earphone. Acoustic occlusion effects were determined by measuring the ear-canal sound pressure produced by a bone-conducted source with and without occlusion by the earphone. The results were compared with measurements obtained from the HDA 200 earphone. Results: Audiometric thresholds obtained using the DD450 earphone did not differ from those obtained with the HDA 200 earphones, indicating that the HDA 200 RETSPLs provided in the audiometer standards (ANSI S3.6-2010; ISO 389-8-2004) are transferable to the DD450. New RETSPLs for the HD 280 Pro earphone were determined from the threshold measurements. Ambient-noise attenuation provided by the DD450 was equivalent to the attenuation provided by the HDA 200. The HD 280 Pro provided less ambient-noise attenuation than the other circumaural earphones, but more than the supra-aural earphones commonly used in audiometry. The DD450 produced an occlusion effect 5 dB larger than that of the HDA 200 at 0.25 and 0.5 kHz; both earphones produced negligible occlusion effects at higher frequencies. The HD 280 Pro produced larger occlusion effects in the low frequencies than the other two earphones, with negligible occlusion effects at 1.0 kHz and above. Conclusions: The HDA 200 RETSPLs are transferable to the DD450. Ambient-noise attenuation and occlusion effects are similar for these two earphones. RETSPLs for the HD 280 Pro are provided. The HD 280 Pro has less ambient-noise attenuation and larger occlusion effects than the DD450 but is a viable low-cost alternative.

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