Audiometric assessment
All audiometric measurements were performed with calibrated instruments in a sound-proof room (DIN EN ISO 8253) by audiologically trained staff. Measurements included standard pure-tone audiometry, performed with a clinical audiometer (AT1000, Auritec, Hamburg, Germany) in 5 dB steps. Pure-tone average (PTA) of the air conduction (AC) and bone conduction (BC) PTA was calculated from AC and BC thresholds at 0.5, 1, 2, and 3 kHz (PTA0.5-3kHz).