(12) United States Patent ao) Patent No.: us 6,418,228 Bi
Terai et al. (45) Date of Patent: Jul. 9,2002
(54) NOISE CONTROL SYSTEM
(75) Inventors: Kenichi Terai, Shijonawate; Hiroyuki Hashimoto, Daitou; Isao Kakuhari, Mino, all of (JP)
(73) Assignee: Matsushita Electric Industrial Co., Ltd., Osaka (JP)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
(21) Appl. No.: 09/353,667
(22) Filed: Jul. 15, 1999
(30) Foreign Application Priority Data
Jul. 16, 1998 (JP) 10-202363
Jun. 4, 1999 (JP) 11-158775
Jun. 4, 1999 (JP) 11-158776
(51) Int. CI.7 H03B 29/00
(52) U.S. CI 381/71.8; 381/71.11
(58) Field of Search 381/71.1, 71.8,
381/71.12, 71.14, 94.1, 94.9, 71.5
(56) References Cited
U.S. PATENT DOCUMENTS
5,278,780 A * 1/1994 Eguchi 708/322
5,337,366 A * 8/1994 Eguchi et al 381/71.11
5,377,276 A * 12/1994 Terai et al 381/71.11
5,388,160 A * 2/1995 Hashimoto et al 381/71.14
5.586.189 A 12/1996 Allie et al.
5.586.190 A 12/1996 Trantow et al.
A noise control system includes: a control sound generator for generating a control sound; an error detector for detecting an error signal between the control sound and noise; a noise detector for detecting a noise source signal; an adaptive filter for outputting a control signal; and a coefficient updator for updating a coefficient of the adaptive filter. The coefficient updator includes at least a first digital filter, a first coefficient update calculator, a second digital filter, a phase inverter, a third digital filter, and a second coefficient update calculator. Alternatively, the coefficient updator includes at least a first digital filter, a second digital filter, a third digital filter, a coefficient update calculator, a phase inverter, a first adder, and a second adder. In either case, the coefficient updator has a function of suppressing an increase in a coefficient gain of the adaptive filter in a predetermined frequency band.
20 Claims, 23 Drawing Sheets