Application of active control technique on a bone conduction headphone for estimating a cross-talk compensation filter

When presenting a stereo sound over a pair of transducers on a bone conduction headphone, the sound wave coming from either the left or right side transducer is delivered directly to the cochlea in both ears. This mechanism is often referred to as 'cross-talk,' and it may decrease the ability to sense sound direction perceived through the bone conduction headphone. In this paper, we investigate the application of active control technique on a bone conduction headphone for estimating a cross-talk compensation filter. To reduce perceived loudness in one of the ears, transfer functions on routes from transducers to a cochlea are estimated by using a microphone placed in the outer ear canal under the assumption that otoacoustic emission (OAE) emitted by the cochlea in response to a bone-conducted sound stimulus can be recorded. By using the transfer functions, the compensation filter which produces anti-sound can be obtained as a result of the filtered-x least mean square (FXLMS) algorithm. In this study, sound stimuli with and without cancellation were presented through a bone conduction headphone where three subjects with normal hearing participated in the measurement. Experimental results show that sound reduction was achieved at the location of the microphone and all participants also reported that they could feel a decrease in the perceived loudness.