Influence of static force on bone conduction threshold measurement.

The influence of static force on bone conduction threshold measurement behavioral bone conduction thresholds are evaluated in clinical settings using a standard headband. The standard headband is designed to apply 5.4 N of static force to the oscillator (ANSI S3.6-1996 R2004), but in practice the static force varies with head size over a range of several Newtons. The influence of the varied force on behavioral thresholds is uncertain. These thresholds have clinical utility in determining the type and severity of hearing loss and research utility in modeling bone-conducted sound pathways. Behavioral bone conduction thresholds for a group of normal-hearing young adult listeners (ages 18–30) were obtained in 1-dB steps as a function of several force levels (2 N, 5 N, variable force) using custom-calibrated and standard headbands for mastoid and forehead oscillator placements across a frequency range from 250 to 8 kHz in sixth-octave bands. No significant differences in behavioral thresholds were obtained as a function of the static force levels tested, although the results supported previous findings that bone conduction thresholds are more sensitive for mastoid than forehead placement. The impact of static force levels on performance for speech understanding with bone conduction listening systems requires further study. [Work supported by AFOSR FA9550-06-0128.]