Research on the design of hear-through controllers for active noise control headphones based on cascade biquad filters considering different directions of sound arrivals

Wearing headphones naturally attenuates the environmental sounds perceived by the human ear, especially for the ones which are designed to be noise-proof, such as active noise control (ANC) headphones. Hear-through (HT) technology actively counteracts this isolation by reproducing environmental sounds at the human ear, so that ambient sounds can be perceived without loss just like the case when not wearing headphones. In this paper, HT is achieved using cascade biquad filters, which has much lower computational burdens than the common FIR filters and thus can increase the battery life. Meanwhile, the single reference microphone is expanded to multiple ones so that the comprehensive HT performance under different directions of sound arrivals can be further enhanced. Both single-channel and multi-channel control strategies are given, in which the controllers are designed with four parametric prototype filters whose parameters are optimized using the differential evolution (DE) algorithm. Simulations and experiments are conducted with a commercial headphone, whose results validate the effectiveness of the proposed methods. Research indicates that the HT performance of the multi-channel control strategy designed using the method proposed in this paper surpasses that of the single-channel control strategy. This finding can also be considered a result of taking into account the spatial characteristics of the microphone array.