A free‐field method to calibrate bone conduction devices.

Abstract

Bone conduction can be valuable for communication applications and can transmit speech reliably whether or not hearing protection is worn. Audiometric standards for bone conduction vibrators focus primarily on a single model of bone vibrator placed at certain locations on the skull. However, a variety of other models and skull locations may be used for communication, so more general calibration methods are needed. Here we developed a method to calibrate bone vibrators, analogous to free‐field methods of air conduction earphone calibration. Participants were seated in an anechoic chamber with a concealed loudspeaker and were fitted with a bone vibrator headset. Participants adjusted bone vibrator voltage output to perceptually match the loudness of third‐octave noise bands played alternately from the bone vibrator and from the loudspeaker. The judgments were made by six participants, each using two different vibrator models and two different skull locations. Data were analyzed and compared to the data obtained using an artificial mastoid. Discussion will focus on how device types, skull locations, and individual variability affect response curves and comparison to the artificial mastoid and on the feasibility of using the described method as a general method for calibrating and assessing vibrator sensitivity. [Work supported by ORAU.]