2.3. Behavioral testing

Participants were seated in a double-walled sound-attenuating booth, providing responses using a button (pure tone audiometry) or mouse and computer monitor (high-frequency audiometry). Air conduction pure tone audiometric thresholds were obtained in accordance with British Society of Audiology recommended procedures (British Society of Audiology, 2011) at 0.25, 0.5, 1, 2, 3, 4, 6, and 8 kHz, using a GSI Arrow audiometer, TDH-39 supra-aural headphones, and MX-41 ear cushions. High-frequency thresholds were obtained using a three-interval, three-alternative, forced-choice paradigm, with stimuli delivered through Sennheiser HDA 200 circum-aural headphones driven by an E-MU 0202 external audio interface. In order to minimize the influence of threshold microstructure and ear canal resonance, stimuli were 1/3-octave bands of noise centered at 10 and 14 kHz. Steady-state duration was 180 ms, with the addition of 10 ms raised-cosine onset and offset ramps. Stimulus level was varied adaptively using a two-down, one-up rule. Threshold was attained using three initial turnpoints (6 dB step size) and eight subsequent turnpoints (2 dB step size). The stimulus level at the final eight turnpoints was averaged to obtain threshold. Thresholds were obtained for each ear separately and then averaged across ears. Prior to testing, each participant performed a practice run containing at least three turnpoints.