Signal characteristics can be altered when sound from environment transmits through earphones to the ear canal. A hear-through filter is usually implemented in an earphone to create a more natural hearing experience. Hear-through filter is also important in augmented reality audio applications. In this paper, a constrained optimal hear-through filter design approach is proposed, where the hear-through filter is designed using a formulation similar to that for a constrained active noise control filter design. One advantage of such a filter design approach is that, compared with the commonly used direct plant response inversion method, the leakage sound around and through earphone will be attenuated in the proposed method, so that the comb-filtering effect is alleviated. Another advantage of the proposed method is that multiple practical constraints can be applied conveniently by formulating a constrained optimization problem and it can be solved efficiently. The proposed design approach can specify the desired delays of reproduced sound in each earphone channel, if a spatial sound impression is desired. The designed hear-through filter can be directly implemented in an active noise control system framework so that the requirement for additional electronic hardware and software components can be minimal for an active noise control earphone.
Hear-through, Transparent mode, Ambient mode, Earphone, Active noise control, Constrained optimal filter design, Convex optimization, Cone programming
Acoustics and Noise Control
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