726 Three-dimensional global active noise control using a delayed driving parametric array loudspeaker

This paper presents a global active noise control method for three-dimensional acoustic field that compensates these disadvantages. Parametric Array Loudspeaker (PAL) in which multiple ultrasonic transducers are placed concentrically is introduced as the control sound source. Driving the ultrasonic transducers with proper time delays, the control sound source produces the wavefront similar to the noise away from the noise source. Superposing the control sound on the original noise sound, and suppressing the sound pressure at the error sensor, sound pressure is suppressed over a wide area around the error sensor. Compared with the case of using a ordinary speaker as the control sources, the validity of the proposed method is clarified.