Acoustic attenuation device with active double wall

• US 5,724,432 A
• Filed: 02/15/1996
• Issued: 03/03/1998
• Est. Priority Date: 05/06/1993
• Status: Expired due to Fees

• Current Assignee: Centre Scientifique Et Technique Du Batiment
• Original Assignee: Centre Scientifique Et Technique Du Batiment
• Inventors: Gagliardini, Laurent, Bouvet, Pascal, Roland, Jacques
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): Mei, Xu
• Application Number:
  US08/535,067
• Time in Patent Office: 747 Days
• Field of Search: 381/71, 381/94
• US Class Current: 381/71.1
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• 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 2210/102 Two dimensional
• CPC Class Codes: G10K 2210/106 Boxes, i.e. active box covering a noise source; Enclosures
• CPC Class Codes: G10K 2210/129 Vibration, e.g. instead of, or in addition to, acoustic noise
• CPC Class Codes: G10K 2210/1291 Anti-Vibration-Control, e.g. reducing vibrations in panels or beams
• CPC Class Codes: G10K 2210/3036 Modes, e.g. vibrational or spatial modes
• CPC Class Codes: G10K 2210/3046 Multiple acoustic inputs, multiple acoustic outputs
• CPC Class Codes: G10K 2210/3219 Geometry of the configuration
• CPC Class Codes: G10K 2210/3223 Materials, e.g. special compositions or gases

Abstract

An active double wall comprises two parallel plates defining a rectangular space. Four sensors are positioned between the plates so as to detect noises in said space, and four actuators are placed between the plates to emit counter-noises in the space. The actuators are phase-controlled by a control unit in order to minimize the sum of the outputs of the sensors. The actuators are respectively positioned at the centers of the sides of the rectangular space, and the sensors are respectively positioned at the centers of the sides of a rhombus whose vertices are the respective centers of the sides of the rectangular space, or vice-versa.

Claims

1. Acoustic attenuation device, comprising two substantially parallel plates defining a rectangularly shaped internal space therebetween, noise detection means arranged between the two plates, inverse noise emission means arranged between the two plates, and control means for controlling the inverse noise emission means in such a way as to minimize a quantity supplied by the noise detection means, wherein the inverse noise emission means comprise four actuators whose respective positions parallel to the plates correspond approximately to four points constituting the centers of respective sides of the rectangular shape of said internal space wherein the noise detection means comprise four sensors whose respective positions parallel to the plates correspond approximately to four points constituting the centers of respective sides of a rhombus whose vertices are the centers of the sides of the rectangular shape of said internal space, wherein the four actuators are controlled in phase, and wherein the quantity to be minimized is represented by the sum of the output signals of the four sensors.

3. Device according to claim 1, wherein the materials and the dimensions of the plates are chosen in such a way as to satisfy the relationships:

f_c /(L_x L_y)² >

800 and f_mrm <

f₂₀₀ or the relationships

f_c /(L_x L_y)² >

300 and f_mrm <

f₂₀₀ /2 in which

f_c, expressed in hertz, denotes a critical frequency of a plate or the larger of two respective critical frequencies of the plates if the plates are of different compositions

L_x and L_y, expressed in meters, are the lengths of the sides of the rectangular shape of the internal space located between the two plates,

f_mrm is a resonant frequency of a mass-spring-mass system, constituted by the two plates and the medium located therebetween, and

f₂₀₀ is an eigenfrequency given by the formula f₂₀₀ =c₀ /max (L_x, L_y), where c₀ denotes the speed of sound in the medium located between the two plates.

4. Device according to claim 1, further comprising a sensor supplying a reference signal, and a band-mass filter to which the reference signal is applied, the output of the bandpass filter being subjected to an adaptive filtering with finite impulse response in order to control the actuators, the band-pass filter allowing frequencies between f_mrm /2 and min(2 f_mrm f₂₀₀) to pass, where

f_mrm is a resonant frequency of a mass-spring-mass system constituted by the two plates and the medium located therebetween, and

f₂₀₀ is an eigenfrequency given by the formula f₂₀₀ =c₀ /max (L_x, L_y), where c₀ denotes the speed of sound in the medium located between the two plates, and L_x and L_y denote the lengths of the sides of the rectangular shape of the internal space located between the two plates.

5. Device according to claim 1, wherein a gas lighter than air occupies the internal space located between the two plates.

6. Device according to claim 5, wherein said gas lighter than air is helium.

2. Acoustic attenuation device, comprising two substantially parallel plates defining a rectangularly shaped internal space therebetween, noise detection means arranged between the two plates, inverse noise emission means arranged between the two plates, and control means for controlling the inverse noise emission means in such a way as to minimize a quantity supplied by the noise detection means, wherein the noise detection means comprise four sensors whose respective positions parallel to the plates correspond approximately to four points constituting the centers of respective sides of the rectangular shape of said internal space, wherein the inverse noise emission means comprise four actuators whose respective positions parallel to the plates correspond approximately to four points constituting the centers of respective sides of a rhombus whose vertices are the centers of the sides of the rectangular shape of said internal space, wherein the four actuators are controlled in phase, and wherein the quantity to be minimized is represented by the sum of the output signals of the four sensors.

7. Device according to claim 2, wherein the materials and the dimensions of the plates are chosen in such a way as to satisfy the relationships:

f_c /(L_x L_y)² >

800 and f_mrm <

f₂₀₀ or the relationships

f_c /(L_x L_y)² >

300 and f_mrm <

f₂₀₀ /2 in which

f_c expressed in hertz, denotes a critical frequency of a plate or the larger of two respective critical frequencies of the plates if the plates are of different compositions

L_x and L_y, expressed in meters, are the lengths of the sides of the rectangular shape of the internal space located between the two plates,

f_mrm is a resonant frequency of a mass-spring-mass system, constituted by the two plates and the medium located therebetween, and

f₂₀₀ is an eigenfrequency given by the formula

f₂₀₀ =c₀ /max (L_x, L_y), where c₀ denotes the speed of sound in the medium located between the two plates.

8. Device according to claim 2, further comprising a sensor supplying a reference signal, and a band-pass filter to which the reference signal is applied, the output of the band-pass filter being subjected to an adaptive filtering with finite impulse response in order to control the actuators, the band-pass filter allowing frequencies between f_mrm /2 and min(2 f_mrm, f₂₀₀) to pass, where

f_mrm is a resonant frequency of a mass-spring-mass system constituted by the two plates and the medium located therebetween, and

f₂₀₀ is an eigenfrequency given by the formula f₂₀₀ =c₀ /max (L_x, L_y), where c₀ denotes the speed of sound in the medium located between the two plates, and L_x and L_y denote the lengths of the sides of the rectangular shape of the internal space located between the two plates.

9. Device according to claim 2, wherein a gas lighter than air occupies the internal space located between the two plates.

10. Device according to claim 9, wherein said gas lighter than air is helium.

11. An acoustic attenuation device comprising two substantially parallel plates defining a rectangularly shaped internal space therebetween, a plurality of noise sensors arranged between the two plates, a plurality of acoustic actuators arranged between the two plates, and control means for controlling the acoustic actuators so as to minimize a sum of output signals of the noise sensors, wherein the acoustic actuators are controlled in phase, and wherein material and dimensions of the two plates are chosen to satisfy at least one relationship selected from the group of relationships consisting of:

F_c /(L_x L_y)² >

800 and f_mrm <

f₂₀₀ /2, and

F_c /(L_x L_y)² >

300 and f_mrm <

f₂₀₀ /2,

wherein F_c, expressed in hertz, denotes one member selected from the group consisting of a critical frequency of one of the two plates and a larger of two respective critical frequencies of the two plates wherein the two plates are of different compositions,

L_x and L_y, expressed in meters, are lengths of sides of a rectangular shape of internal space located between the two plates,

f_mrm is a resonant frequency of a mass-spring-mass system, comprising the two plates and medium located therebetween, and

f₂₀₀ is an eigenfrequency given by the formula F₂₀₀ =C₀ /max (L_x, L_y) where so denotes speed of sound in medium located between the two plates.

12. The device according to claim 11, further comprising a reference signal sensor supplying a reference signal, and a band-pass filter to which the reference signal is applied, the output of the band-pass filter being subjected to an adaptive filtering with finite impulse response in order to control the acoustic actuators, the band-pass filter allowing frequencies between f_mrm /2 and rain(2 f_mrm, f₂₀₀) to pass.

13. The device according to claim 11, wherein a gas lighter than air occupies internal space located between the two plates.

14. The device according to claim 13, wherein said gas lighter than air is helium.

15. An acoustic attenuation device comprising two substantially parallel plates defining a rectangularly shaped internal space therebetween, a plurality of noise sensors arranged between the two plates, a plurality of acoustic actuators arranged between the two plates, and control means for controlling the acoustic actuators so as to minimize a sum of output signals of the plurality of noise sensors and wherein the acoustic actuators are controlled in phase, reference signal sensor supplying a reference signal, and a band-pass filter to which the reference signal is applied, wherein output of the band-pass filter is subjected to an adaptive filtering with finite impulse response to control the acoustic actuators, the band-pass filter allowing frequencies between f_mrm /2 and min(2 f_mrm, f₂₀₀) to pass, wherein

f_mrm is a resonant frequency of a mass-spring-mass system comprising the two plates and medium located therebetween, and

f₂₀₀ is an eigenfrequency given by the formula f₂₀₀ =C₀ /max (L_x, L_y), where co denotes the speed of sound in medium located between the two plates, and L_x and L_y denote lengths of sides of a rectangular shape of internal space located between the two plates.

16. The device according to claim 15, wherein a gas lighter than air occupies internal space located between the two plates.

17. The device according to claim 16, wherein said gas lighter than air is helium.