Frequency characteristics of bone conduction actuators - Measurements of loudness and acceleration

Loudness as a subjective measurement and acceleration as an objective measurement were taken to measure the frequency characteristics of four different bone conduction actuators. The loudness of bone conduction was measured by balancing bone-conducted stimuli at 17 frequencies from 0.2 kHz to 8 kHz. The acceleration at equal loudness, which was measured by a Brüel & Kjær 4930 artificial mastoid, was transferred to relative levels for comparison with the loudness measurements. A relationship between loudness and acceleration was difficult to find for a bone conduction actuator of inner-ear type while for a head-of-mandible type, a relationship was found at some frequencies. Furthermore, otoacoustic emission of a head-of-mandible actuator was measured. It was hypothesized that loudness can be estimated by objective measurements of bone conduction actuators at specific frequencies.