  Active noise control (ANC) has been widely utilized to reduce unwanted
environmental noise. The primary objective of ANC is to generate an anti-noise
with the same amplitude but the opposite phase of the primary noise using the
secondary source. However, the effectiveness of the ANC application is impacted
by the speaker's output saturation. This paper proposes a two-gradient
direction ANC algorithm with a momentum factor to solve the saturation with
faster convergence. In order to make it implemented in real-time, a
computation-effective variable step size approach is applied to further reduce
the steady-state error brought on by the changing gradient directions. The time
constant and step size bound for the momentum two-gradient direction algorithm
is analyzed. Simulation results show that the proposed algorithm performs
effectively in the time-unvaried and time-varied environment.
