Acoustics – Sound-modifying means – By wave interference
Patent
1994-05-24
1996-08-27
Dang, Khanh
Acoustics
Sound-modifying means
By wave interference
381 71, F01N 106
Patent
active
055503349
DESCRIPTION:
BRIEF SUMMARY
In the design of active noise controlled mufflers a common problem is the resulting lengthy extension which protrudes beyond the main enclosure to the end of the vehicle resulting in an unattractive "snout". Beyond the physical undesirability of this extension there is a more serious problem created and that is the large acoustic air mass that resides in the snout. As this air mass is extremely difficult to move to and fro at high frequencies the result is a small amount of anti-sound being generated.
To overcome this problem it is proposed to keep the extension or snout short which reduces the moving mass. The solution has typically resulted in a configuration that has a very short link between the loudspeaker and the pipe and wherein the loudspeaker is typically placed far from the engine for the benefit of reduced sound pressure and temperature. The controller can then cancel the exhaust noise provided only one acoustic mode can propagate in the exhaust pipe over the control bandwidth. The loudspeaker enclosure volume may be reduced somewhat and the diameter of the tail-pipe need not be larger than normal. The problems with this solution were that the loudspeaker is subjected to high temperatures as well as the corrosive effects of exhaust gases.
To solve these residual problems the instant invention manipulates the mean flow of the exhaust gases to cool the loudspeaker enclosure. Either a full or partial venturi is used to generate an area that is below atmospheric pressure. A bleed pipe allows ambient air to flow into this area thereby counteracting the flow of exhaust gases into the speaker area. A filter can be provided in the bleed pipe to reduce the radiated noise. Additionally a heat shield can be employed to protect the loudspeaker from the exhaust pipe or, instead, a reflective coated layer that conducts sound. To prevent a sudden reversal of the cooling air the configuration is designed to allow the cooling flow to maintain the exhaust gas concentration in the front cavity at a reasonable level. A diffuser section can be used to accomplish this as well as a contracted section followed immediately by an expansion section. Cooling can also be accomplished by using the cooling fluid of the vehicle or by using separate fans. Both would entail additional expenditures and add a degree of complexity to the configuration.
Therefore, it is an object of this invention to provide an improved muffler that eliminates the long loudspeaker enclosure.
Another object of this invention is to provide an actively controlled noiseless muffler having a short connection between the exhaust pipe and the loudspeaker enclosure.
A further object of this invention is to an active noise cancellation system for an exhaust system wherein the diameter/size of the exhaust pipe can be of standard size.
A still further object of this invention is to provide an actively controlled muffler configuration that prevents ingestion of exhaust gases into the loudspeaker enclosure.
Yet another object of this invention is the provision of a venturi means in an active noise cancellation exhaust system to create a differential pressure adjacent the speaker enclosure.
These and other objects of this invention not specifically enumerated herein will become apparent as reference is made to the following detailed discussion and drawings in which
FIG. 1 is a diagrammatic view of a standard active noise cancellation muffler, and
FIG. 2 is a diagrammatic view of an improved configuration of an improved active noise cancellation muffler system and
FIG. 3 is a diagrammatic view of an in-pipe or venturi configuration in an improved active noise cancellation muffler, and
FIG. 4 is a diagrammatic view of a venturi nozzle configuration in an active noise cancellation muffler to reduce radiation heating, and
FIG. 5 is another diagrammatic view of an in-pipe or venturi configuration in an improved active noise cancellation muffler showing a separate heat shield, and
FIG. 6 is a diagrammatic view of a partial venturi nozzle configuration in an active nois
REFERENCES:
patent: 5044464 (1991-09-01), Bremigan
patent: 5088575 (1992-02-01), Eriksson
patent: 5097923 (1992-03-01), Ziegler et al.
Dang Khanh
Noise Cancellation Technologies, Inc.
LandOfFree
Actively sound reduced muffler having a venturi effect configura does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Actively sound reduced muffler having a venturi effect configura, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Actively sound reduced muffler having a venturi effect configura will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1057510