ACTIVE CONTROL OF A MOVING NOISE SOURCE—EFFECT OF OFF-AXIS SOURCE POSITION

✍ Scribed by J. GUO; J. PAN; M. HODGSON

• Book ID: 102975844
• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 795 KB
• Volume: 251
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.2001.3994

✦ Synopsis

An optimally arranged multiple-channel active-control system is known to be able to create a large quiet zone in free space for a stationary primary noise source. When the primary noise source moves, the active control of the noise becomes much more di$cult, as the primary noise "eld changes with time in space. In this case, the controller of the control system must respond fast enough to compensate for the change; much research has been focused on this issue. In this paper, it is shown that a moving source also causes di$culties from an acoustical perspective. A moving source not only changes continuously the strengths and phases of the sound "eld in the space, but also changes the wavefront of the primary sound "eld continuously. It is known that the e$ciency of active noise control is determined mainly by the wavefront matching between the primary and control "elds. To keep the control system e!ective in the case of a moving source, the wavefront of the control "eld needs to change, in order to continuously match the primary-wavefront change. This paper shows that there are limitations to the control-wavefront change. An optimally pre-arranged, multiple-channel control system is not able to construct a matching wavefront when the primary source moves outside a certain range. In other words, the control system is still able to create a large quiet zone only when the primary source moves within a range around the central axis of the control system. Both the location and the size of the quiet zone change with the location of the primary source.

2002 Elsevier Science Ltd.