Gsi 61 audiometer

Air conduction thresholds were obtained for pulsed tones using a GSI-61 audiometer (Grason-Stadler, Inc.) and ER3A insert earphones (Etymotic Research, Inc.) in frequencies from 250 to 8000 Hz, whereas HDA200 earphones (Sennheiser Electronic Corp.) were used for testing the extended high frequencies (EHFs) above 8000 Hz. Bone conduction thresholds were obtained at octave frequencies 500 to 4000 Hz to establish the nature of the loss, if present. Air conduction thresholds in each ear were averaged across frequencies to yield three distinct pure-tone averages (PTAs) for analysis: (1) clinical PTA of 500, 1000, and 2000 Hz; (2) high-frequency PTA (HF-PTA) of 3000, 4000, 6000, and 8000 Hz; and (3) EHF-PTA of 10,000, 12,500, and 14,000 Hz. Thresholds at 250 Hz were analyzed separately. Any threshold that exceeded the limits of the audiometer was set to 110 dB HL for inclusion in the mean. Only one participant, an older individual with diabetes, had a no-response in the conventional audiometric frequency range that had to be set to 110 dB HL for inclusion in the mean calculation. It was at a single frequency (8000 Hz) in one ear. In the EHF range, “no-response” was obtained in a slightly greater number of subjects with diabetes (14/57 or 25%) than without diabetes (8/50 or 16%), respectively.

Ability to recognize speech in background noise was measured using the QuickSIN (Killion et al., 2004 (link)) administered binaurally via insert (ER-3) earphones. The test consisted of low-context sentences spoken by a female talker. Each sentence includes five key words (e.g., “Tend the sheepwhile the dogwanders”). Six sentences were presented, one each at signal-to-noise ratios from +25 dB to 0 dB in 5 dB steps. In each case the background noise was four-talker babble (3 males, 1 female). The test was recorded on compact disc and routed through a Grason-Stadler GSI-61 audiometer. As specified by the protocol for the QuickSIN, speech levels were set to 70 dB HL for most listeners and to a “loud but ok” level for subjects with a pure-tone average of 50 dB HL or greater in either ear. The levels judged to be “loud but ok” ranged from 75-85 dB HL. The test score represents the signal-to-noise ratio required for the listener to repeat 50% of the words correctly. One practice list and two test lists were presented for each participant, and the two test list scores were averaged for a final score.

Thirty-six normal-hearing native speakers of American English between 18 and 34 years of age (mean = 22.72 years, SD = 3.51 years, 6 (17%) male) took part in our experiments. All participants were recruited from a population of students at the University of Iowa. Pure-tone hearing thresholds were measured using a GSI-61 audiometer (Grason-Stadler Inc., Littleton, MA) through TDH-39P circum-aural headphones (Telephonics Corporation, Farmingdale, NY) at octave frequencies from 250 to 8000 Hz as well as at 3, 6, and 12 kHz (Figure 1). The pure-tone thresholds at 0.5, 1, 2, and 4 kHz no greater than 20 dB HL, as well as hearing symmetry within 20 dB for any tested frequency, were used as our hearing screening criteria. All study procedures were reviewed and approved by the University of Iowa Institutional Review Board. All work was carried out in accordance with the Code of Ethics of the World Medical Association (Declaration of Helsinki), and written informed consent was obtained for everyone.