Design of a feedback controller for active noise control with in-ear headphones

This paper presents a method to design optimal feedback controllers for active noise control. It also shows the main problem of in-ear headphones, namely, interpersonal variances, and its possible solution. These variances make the design of stable feedback controllers with good noise attenuation difficult. To solve this problem we measured the secondary paths of a few test persons and divided these transfer functions into their minimum-phase and their allpass part using the complex cepstrum. In this context we show that the allpass part is almost constant. Thus, it is possible to generate an optimal controller for a given disturbance using the internal model control technique. After that the interpersonal variances will be partly compensated by a mean inverse minimum-phase transfer function. The result is a stable controller with a good noise attenuation for all test persons.