Active sound attenation system for engine exhaust systems and the like

• US 5,097,923 A
• Filed: 11/07/1989
• Issued: 03/24/1992
• Est. Priority Date: 02/19/1988
• Status: Expired due to Term

• Current Assignee: NCT Group, Inc.
• Original Assignee: Noise Cancellation Technologies, Inc. (NCT Group, Inc.)
• Inventors: Gardner, John W., Ziegler, Eldon W.
• Primary Examiner(s): Brown, Brian W.
• Application Number:
  US07/435,499
• Time in Patent Office: 868 Days
• Field of Search: 181/206, 181/207, 181/227, 181/250, 181/269, 381/71
• US Class Current: 181/206
• CPC Class Codes: F01N 1/065 by using an active noise source, e.g. speakers
• CPC Class Codes: F01N 1/22 the parts being resilient walls
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17861 using additional means for damping sound, e.g. using sound absorbing panels
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 11/17883 the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed
• CPC Class Codes: G10K 2210/12822 Exhaust pipes or mufflers
• CPC Class Codes: G10K 2210/3227 Resonators
• CPC Class Codes: G10K 2210/32272 Helmholtz resonators

Abstract

An active sound attenation system for combustion engine exhaust systems and the like is disclosed. To protect the counter-noise acoustic wave generator from the environment of the medium propagating the undesirable noise, an acoustically tuned anti-noise chamber is interposed between the wave generators 19, 19A and the location of the medium with the undesirable noise. To provide for global cancellation at the outlet end 4, of the exhaust pipe 10, the anti-noise chamber 11, 11A has an annular opening disposed substantially in the plane 4 of the exhaust pipe outlet thereby giving the undesirable noise and the cancelling noise an apparent common source.

Claims

1. An active noise suppression system for exhaust of a combustion engine comprising:

an exhaust transfer pipe, coupled to the combustion engine and having first and second ends, for transferring exhaust gas in a first direction from the combustion engine to ambient atmosphere, said first end receiving the exhaust gas from the combustion engine and said second end emitting the exhaust gas to the ambient atmosphere;

an anti-noise chamber, annularly surrounding an outer periphery of said exhaust transfer pipe and having an outlet open to the ambient atmosphere adjacent said second end of said exhaust transfer pipe, for projecting anti-noise sound waves through said outlet to the ambient atmosphere;

an anti-noise speaker, mounted to said anti-noise chamber for communication therewith, for generating and projecting said anti-noise sound waves into said anti-noise chamber to cancel noise generated by the combustion engine exhaust;

separation means for isolating said anti-noise chamber from exhaust gas.

2. An active noise suppression system according to claim 1 further comprising another anti-noise speaker, said anti-noise speakers being disposed on said anti-noise chamber at opposed axial positions with respect to said exhaust transfer pipe upstream of said second end of said exhaust transfer pipe.

3. An active noise suppression system according to claim 2, wherein said anti-noise chamber is acoustically tuned and has a large diameter section joined to a smaller diameter section, said anti-noise speakers being mounted to said large diameter section, said smaller diameter section extending along said exhaust transfer pipe to said second end.

4. An active noise suppression system according to claim 3, wherein a front end of said large diameter section is closed off by an annular plate connected to an outer position of said exhaust transfer pipe, an outlet end of said smaller diameter section serving as said outlet of said anti-noise chamber which is supported from said exhaust transfer pipe by radially extending support plates.

5. An active noise suppression system according to claim 1, wherein said anti-noise chamber is symmetrically configured with respect to a longitudinal axis through a center of said exhaust transfer pipe.

6. An active noise suppression system according to claim 5, wherein said exhaust transfer pipe and said anti-noise chamber are cylindrical and concentric with respect to said longitudinal axis.

7. An active noise suppression system according to claim 1, further comprising a cooling chamber, disposed annularly between said exhaust transfer pipe and said anti-noise chamber, for drawing cooling air from the ambient atmosphere into said exhaust transfer pipe to cool said exhaust gas within said exhaust transfer pipe, said separation means comprising an outer wall of said cooling chamber.

8. The active noise suppression system according to claim 7, wherein said cooling chamber draws cooling air inward from adjacent said second end of said exhaust transfer pipe to flow in a second direction opposite the flow of exhaust gas through said exhaust transfer pipe in said first direction.

9. An active noise suppression system according to claim 8, wherein said exhaust transfer pipe has air flow openings for passing said cooling air from said cooling chamber into said exhaust transfer pipe, said air flow openings being symmetrically disposed about a circumference of said exhaust transfer pipe.

10. An active noise suppression system according to claim 9, wherein said air flow openings comprised of at least four separate radial openings.

11. An active noise suppression system according to claim 9, wherein said air flow openings are comprised of eight separate radial openings.

12. The active noise suppression system according to claim 1, wherein said combustion engine is an internal combustion engine.

13. An active noise suppression system according to claim 12, wherein the combustion engine being a driving engine for a motor boat.

14. An active noise suppression system according to claim 12, wherein the combustion engine is a driving engine for a motorized road passenger vehicle.

15. An active noise suppression system according to claim 1, wherein the combustion engine has an exhaust pipe for delivering the exhaust gas to said first end of said exhaust transfer pipe, said first end of said exhaust transfer pipe being insertable into said exhaust pipe and permanently affixable thereto by clamping seal means.

16. An active noise suppression system according to claim 15, wherein said exhaust transfer pipe, said anti-noise chamber and said anti-noise speakers are integrally constructed within a unitary sheet metal housing.

17. The active noise suppression system of claim 1, wherein said separation means comprises an outer wall of said exhaust transfer pipe.

18. An active noise suppression system for exhaust of a combustion engine comprising:

an exhaust transfer pipe, coupled to the combustion engine and having first and second ends, for transferring exhaust gas in a first direction from the combustion engine to ambient atmosphere, said first end receiving exhaust gas from the combustion engine and said second end emitting the exhaust gas to the ambient atmosphere;

passive noise reduction means surrounding an outer periphery of said exhaust transfer pipe, for reducing noise generated by the combustion engine and exhaust gas turbulence by cooling the exhaust gas within said exhaust transfer pipe;

active noise reduction means for attenuating noise generating by the combustion engine and exhaust, said active noise reduction means comprising

an anti-noise chamber surrounding an outer periphery of said passive noise reduction means, having an outlet port open to the ambient atmosphere adjacent said second end of said exhaust transfer pipe, for projecting anti-noise sound waves through said outlet port to the ambient atmosphere,

an anti-noise speaker, mounted to said anti-noise chamber, for generating and projecting said anti-noise sound waves into said anti-noise chamber to further reduce noise generated by the combustion engine and exhaust; and

separation means for isolating said anti-noise chamber from exhaust gas.

19. The active noise suppression system of claim 18, further comprising plural anti-noise speakers mounted to said anti-noise chamber.

20. The active noise suppression system of claim 18, wherein said passive noise reduction means comprises a cooling chamber having an outlet end open to the ambient atmosphere for drawing inward cooling air from the ambient atmosphere.

21. The active noise suppression system of claim 20, wherein exhaust transfer pipe has air flow openings arranged around an outer periphery thereof near said first end for drawing said cooling air from said cooling chamber into said exhaust transfer pipe to reduce turbulence of the exhaust gas to reduce noise.

22. The active noise suppression system of claim 18, wherein said exhaust transfer pipe is provided with air flow openings communications with said passive noise reduction means.

23. The active noise suppression system of claim 21, wherein said exhaust transfer pipe, cooling chamber, anti-noise chamber and anti-noise speakers are integrally constructed within a unitary sheet metal housing.

24. The active noise suppression system of claim 23, wherein said combustion engine has an exhaust pipe for delivering the exhaust gas to said first end of said exhaust transfer pipe, said first end being insertable into said exhaust pipe and affixable thereto permanently by sealing clamp means.

25. The active noise suppression system of claim 18, wherein said anti-noise chamber is acoustically tuned and comprises a first section of large diameter coupled to a second section of smaller diameter, said anti-noise speakers comprising two speakers mounted to an outer periphery of said first section 180°

apart from each other.

26. The active noise suppression system of claim 18, wherein said exhaust transfer pipe, passive noise reduction means, active noise reduction means and anti-noise speakers are integrally constructed within a unitary sheet metal housing.

27. The active noise suppression system of claim 18, wherein said separation means comprises an outer wall of said passive noise reduction means.

28. An integrally housed anti-noise suppression system comprising:

an exhaust transfer pipe having first and second ends, for transferring exhaust gas in a first direction from a combustion engine to ambient atmosphere, said first end receiving exhaust gas from an exhaust pipe of the combustion engine and said second end emitting the exhaust gas to the ambient atmosphere;

an anti-noise chamber, surrounding an outer periphery of said exhaust transfer pipe and having an outlet port open to the ambient atmosphere adjacent said second end of said exhaust transfer pipe, for projecting anti-noise sound waves through said outlet to the ambient atmosphere;

an anti-noise speaker, mounted to an outer periphery of said anti-noise chamber, for generating and propagating said anti-noise sound waves into said anti-noise chamber to cancel noise generated by said combustion engine and said exhaust pipe; and

separation means for isolating said anti-noise chamber from exhaust gas,

said exhaust transfer pipe, anti-noise chamber and anti-noise speakers are constructed and integrally housed within a sheet metal structure.

29. The integrally housed anti-noise suppression system of claim 28, wherein, said first end of said exhaust transfer pipe is insertable and permanently affixable by clamp sealing means to said exhaust pipe.

30. The integrally housed anti-noise suppression system of claim 29, further comprising:

a cooling chamber, disposed annularly between said exhaust transfer pipe and said anti-noise chamber and having an outlet end open to the ambient atmosphere, for drawing cooling air inward from the ambient atmosphere, said separation means comprising an outer wall of said cooling chamber.

31. The integrally housed anti-noise suppression system of claim 30, wherein said cooling air is drawn into said cooling chamber in a second direction opposite to said first direction of exhaust gas flow within said exhaust transfer pipe.

32. The integrally housed anti-noise suppression system of claim 28, further comprising an additional anti-noise speaker mounted to an outer periphery of said anti-noise chamber, wherein said anti-noise chamber is acoustically tuned and has a first section of large diameter coupled to a second section of smaller diameter, said anti-noise speakers operatively coupled to an outer periphery of said first section 180°

apart from each other.

33. The integrally housed anti-noise suppression system of claim 31, wherein said separation means comprises an outer wall of said exhaust transfer pipe.