# Directional Suppression of Monotone Noises with A Parametric Array Loudspeaker
); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (Y.L).1 School of Microelectronics, Tianjin University, Tianjin 300072, China; [EMAIL_ADDRESS] (J.  
sources\", to generate canceling signals with similar amplitudes while opposite in phase to the noises. To date, ANC schemes mainly follow feedforward [14; 15] and feedback [16; 17] approaches. A single-channel feedforward system is the classic ANC algorithm consisting of a reference microphone to detect the noise to be canceled and an error microphone to monitor the system performance by detecting the residual error [8]. When sensing or estimating the target noise as the reference signal is not possible, the feedback approach is required in the ANC architecture. This paper mainly focuses on the feedforward approach for its robustness from straightforward environmental noise measurement. The key to feedforward ANC implementation is the effective estimation of the secondary path, which is understood as an adaptive filter to produce a phase-countering sound for the noise canceling at the error microphone. Currently, the most-preferred filter iteration technique is the filtered-x least mean square (FxLMS) algorithm [18] for its efficiency in computation and robustness for either single-channel or multi-channel applications [14; 19; 20]. Current ANC systems mainly use conventional voice coil loudspeakers (VCLs) as secondary sources. However, the omnidirectional nature of VCLs may induce adverse effects, such as the increment in the sound pressure level (SPL) in neighboring areas apart from the target position [21] and undesired acoustic feedback into the reference microphone [22].