Acoustic Equalization for Headphones Using a Fixed Feed-forward Filter

The headphones market is expanding and new applications based on active noise control (ANC) are emerging. In this contribution, we derive a fixed feed-forward FIR filter for ANC headphones based on a minimum mean-square error (MMSE) cost function that realizes user-defined active equalization and attenuation of the ambient sound. By analyzing the limit of this solution with respect to active attenuation, we derive a generalized solution that allows the user to influence the equalization even for high attenuation. We investigate the importance of a priori information and runtime measurements of the acoustic transfer functions, and show how this can be utilized to further increase the accuracy of the equalization.