Equivalent threshold sound pressure levels (ETSPLs) for Oscilla H210A circumaural audiometric headphones.

OBJECTIVE: To determine ETSPLs for the Oscilla H210A circumaural audiometric headphones. DESIGN: ETSPL measurements were performed for 11 audiometric frequencies with the ISO 8253-1 (2010) bracketing procedure. STUDY SAMPLE: The study was based on 25 otologically normal test subjects. RESULTS: ETSPLs are provided for an ear simulator according to IEC 60318-1 (2009) along with a detailed measurement uncertainty budget. CONCLUSIONS: ETSPLs for the Oscilla H210A headphones may be used to update ISO 389-8 (2004), the reference ETSPL standard for circumaural audiometric headphones.

Influence of response-time limits on automated hearing threshold determination.

OBJECTIVE: In automated hearing threshold determination procedures, prespecified response- time limits can be applied to evaluate whether a stimulus was truly heard by checking whether the test subject reacts to the onset and the offset of the stimuli within given time intervals. The influence of different response-time limits on the threshold of normal-hearing test subjects was investigated. DESIGN: Two-stage hearing threshold level measurements applying the ISO 8253-1 (2010) bracketing procedure were performed. Pre-tests at 125 Hz and 1000 Hz were carried out with maximum accepted response times of 600 ms, 1000 ms, and 1200 ms. Subsequently, thresholds were measured at the seven octaves between 125 Hz and 8000 Hz with maximum accepted response times of 600 ms and 1000 ms. STUDY SAMPLE: 15 test subjects in pre-tests, 25 test subjects in the main study. RESULTS: Threshold levels determined with a maximum accepted response time of 1000 ms are 2.6 dB lower than those obtained with a maximum accepted response time of 600 ms (95% CI -1.6 dB to 6.9 dB). The threshold shift was similar at all frequencies. CONCLUSIONS: Based on this study, response-time limits after both stimulus onset and offset of at least 1000 ms are recommended.

Dependence of binaural gain for infrasound on interaural phase difference.

Increasing complaints about infrasound have generated interest in understanding its perception, including binaural effects. This study investigated the level difference between monaural and binaural presentation required for detection and equal loudness (binaural gain) for pure tones with frequencies of 8, 32, and 400 Hz and an 8 Hz sinusoidally amplitude-modulated tone with diotic 400 Hz carrier. Monaural stimuli were compared to binaural stimuli with interaural phase differences (IPDs) of 0°, 90°, and 180° in two experiments: absolute threshold measurements and loudness matching at 40 phons. The latter was repeated with transposed tones (400 Hz carrier multiplied by a half-wave-rectified 8 Hz sinusoid). When expressed as differences in sound pressure level, similar binaural gain was found across all stimulus types under the diotic condition. Confirming previous studies, the gain was larger at supra-threshold levels (40 phons) than at threshold. However, when the loudness-matching results were expressed as binaural gain with respect to the loudness level, they became 17.5, 11.2, and 5.8 phons for the 8, 32, and 400 Hz stimuli, respectively. Results for the 8 Hz pure tone and the transposed stimulus were IPD dependent.