Active broadband sound quality control algorithm with accurate predefined sound pressure level

The aim of conventional active noise control (ANC) system is to attenuate the sound pressure level (SPL) of unwanted noise as much as possible. However, it is desirable to retain some of the sound with a specified spectrum to meet the requirements of human perception in various applications. This is particularly true in automotive vehicle applications in which some engine noise is to be retained. An active noise equalizer (ANE) is proposed to meet this requirement. This paper proposes an active broadband sound quality control algorithm, based on traditional broadband ANE. The algorithm can not only shape the spectrum of the residual noise according to the sound quality filter, but also control the SPL of the residual noise to satisfy a predefined target accurately, when the amplitude of the disturbance noise changes. This aim is accomplished by introducing a gain factor which is adaptively determined based on the power of the instantaneous disturbance noise and the predefined target. This algorithm has four control modes according to the value of the gain factor. Simulations are carried out to validate the performance of the proposed algorithm using both simulated noise and real vehicle cabin noise. Simulation results show that the SPL error of the proposed control algorithm is within ±2 dB of the predetermined target in the majority of cases simulated. The tracking capability of the proposed algorithm is shown to exhibit good performance in the presence of a time varying SPL target and time varying disturbance noise.