Theoretical explanation of uneven frequency response of time-domain acoustic contrast control method

Acoustic contrast control (ACC) is one of the most commonly utilized sound zone control methods, which maximizes the ratio of the average squared sound pressure in two control zones. The time-domain formulation of ACC (TACC) is usually preferred since it can optimize the whole bandwidth in a single step and the resulting control filter is guaranteed to be causal. Many researchers have noted that TACC suffers from uneven frequency response. However, a convincing theoretical explanation of this problem is yet to be investigated. In this letter, an asymptotically equivalent frequency-domain form of TACC is constructed, based on which it can be proven that TACC has the tendency of extracting the specific frequency component with the highest contrast. Simulation results validate the efficacy of this theoretical analysis.