Estimation of cross-talk compensation filter using bone conduction ear microphone

Having a bone conduction (BC) transducer anywhere on the head will result in a BC sound reaching the cochlea in both ears. This “cross-talk” phenomenon may limit a listener's ability with a pair of BC transducer to sense sound direction. In this paper, we discuss a way to minimize cross-talks in BC sound reproduction using a method called “cross-talk cancellation.” Ideally, the method requires transfer functions (TFs) from each of the BC transducers to each of the listener's cochleae to accurately synthesize cross-talk compensation (CTC) filters; however, a direct measurement of the TFs at the cochlea is not possible. Since the ear canal is the closest to the cochlea, we thus hypothesize that the TFs measured at the ear canal might be used to achieve cross-talk cancellation at the cochlea in the inner ear. Therefore, we utilized a BC ear microphone to capture the vibration of the bony ear-canal caused by vibrating transducers on the mastoid. The filtered-x least mean square (FxLMS) algorithm was then used to estimate the CTC filter. Experiments with and without cross-talk cancellation were done to determine the effective frequency range that could achieve cancellation in the ear canal of three normal-hearing participants.