NOISE CONTROL DEVICE

• US 20080317254A1
• Filed: 06/20/2008
• Published: 12/25/2008
• Est. Priority Date: 06/22/2007
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: KANO, Hiroyuki
• Granted Patent: US 8,170,227 B2
• Time in Patent Office: Days
• US Class Current: 381/71.4
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 2210/12 Rooms, e.g. ANC inside a room, office, concert hall or automobile cabin
• CPC Class Codes: G10K 2210/1281 Aircraft, e.g. spacecraft, airplane or helicopter
• CPC Class Codes: G10K 2210/1282 Automobiles
• CPC Class Codes: G10K 2210/1283 Trains, trams or the like
• CPC Class Codes: G10K 2210/3214 Architectures, e.g. special constructional features or arrangements of features

Abstract

A noise control device according to the present invention comprises: four or more noise detectors each for detecting a plurality of noises arriving thereat, and outputting the noises as a noise signal; a control speaker for radiating, to a control point, a control sound based on each noise signal; and a filter section for signal-processing noise signals from the noise detectors by using filter coefficients which respectively correspond to the four or more noise detectors and which are set such that the control sound from the control speaker reduces the plurality of noises arriving at the control point, and for adding up all the signal-processed noise signals, and for outputting a resultant signal to the control speaker. The control point and the control speaker are provided within a polyhedral-shaped space whose apexes are placement positions of the noise detectors.

Claims

1. A noise control device for reducing a plurality of noises arriving at a control point by radiating a control sound to the control point, the noise control device comprising:

four or more noise detectors each for detecting the plurality of noises arriving thereat, and outputting the detected noises as a noise signal;

a control speaker for radiating, to the control point, the control sound based on each noise signal; and

a filter section for signal-processing noise signals from the noise detectors by using filter coefficients which respectively correspond to the four or more noise detectors and which are set such that the control sound from the control speaker reduces the plurality of noises arriving at the control point, and for adding up all the signal-processed noise signals, and for outputting a resultant signal to the control speaker, wherein

the control point and the control speaker are provided within a polyhedral-shaped space whose apexes are placement positions of the noise detectors.

2. The noise control device according to claim 1, wherein

the filter coefficients are fixed coefficients, and

the noise detectors each have a distance from an adjacent noise detector, the distance corresponding to an upper-limit frequency of a predetermined control band.

3. The noise control device according to claim 2, wherein a relationship a≦

c/2f is realized when the distance from the adjacent noise detector is a, a sound velocity is c, and the upper-limit frequency of the control band is f.

4. The noise control device according to claim 2, wherein a relationship a≦

c/3f is realized when the distance from the adjacent noise detector is a, a sound velocity is c, and the upper-limit frequency of the control band is f.

5. The noise control device according to claim 2, wherein the filter coefficients are calculated using a transfer function between the control speaker and the control point, such that a difference between the control sound arriving at the control point and a sum of the plurality of noises arriving at the control point is minimum.

6. The noise control device according to claim 5, wherein the filter coefficients are calculated in a room which simulates an acoustic field which is a place of use of the noise control device.

7. The noise control device according to claim 5, wherein the filter coefficients are each a general solution for the plurality of noises arriving at the control point.

8. The noise control device according to claim 1, wherein the filter coefficients are adaptively updated using a transfer function between the control speaker and the control point, such that a difference between the control sound arriving at the control point and a sum of the plurality of noises arriving at the control point is minimum.

9. The noise control device according to claim 1, wherein the polyhedral-shaped space has an approximately spherical shape.

10. The noise control device according to claim 1, wherein the polyhedral-shaped space has an approximately circular cylindrical shape.

11. The noise control device according to claim 1, wherein a relationship r−

d≧

τ

·

c is realized for each of the noise detectors in the case where a time required for the plurality of noises to be, after being detected by each of the noise detectors, radiated as the control sound from the control speaker is τ

, a sound velocity is c, a distance between the control point and each of the noise detectors is r, and a distance between the control speaker and the control point is d.

12. The noise control device according to claim 1, wherein the noise control device is provided on a seat so as to reduce the plurality of noises arriving near the seat which is the control point,

the noise control device further comprising a plurality of arms, to each of which the noise detectors are attached and which are attached to the seat such that the control point and the control speaker are positioned within the space.

13. The noise control device according to claim 12, wherein

the control point is set to be near ears of a listener seated on the seat, and

the control speaker is provided near the control point.

14. The noise control device according to claim 12, wherein the arms are attached to the seat such that the arms are shiftable,

the noise control device further comprising:

a pressure sensor which is attached to at least one of a bottom of the seat and a backrest of the seat; and

arm shifting means for, when a pressure detected by the pressure sensor has a predetermined value or higher, shifting the arms such that the control point and the control speaker are positioned within the space, and for, when the pressure detected by the pressure sensor has a smaller value than the predetermined value, shifting the arms such that the control point and the control speaker are not positioned within the space.

15. The noise control device according to claim 12, wherein the seat is provided with a seatbelt,

the arms are attached to the seat such that the arms are shiftable,

the noise control device further comprising:

determination means for determining whether or not the seatbelt is fastened; and

arm shifting means for, when the determination means determines that the seatbelt is fastened, shifting the arms such that the control point and the control speaker are positioned within the space, and for, when the determination means determines that the seatbelt is not fastened, shifting the arms such that the control point and the control speaker are not positioned within the space.