Noise reduction apparatus and method

Claim 2

Apparatus for separating acoustic energy in the form of waves from a moving fluid, comprising: a. a duct adapted to carry said fluid and said acoustic energy; b. means forming a chamber adjacent said duct separated froms said duct by a wall; and c. at least a pair of coupling elements in said wall spaced apart along the path of said acoustic energy a distance approXimately equal to an odd multiple of one-quarter wave length of the frequency of the wave to be separated and sized to couple a predetermined substantial portion of said acoustic energy from said duct into said chamber, said coupling elements further being sized in relationship to one another so that the energy being coupled is coupled with a high degree of directivity.

Claim 3

Muffler apparatus for attenuating acoustic energy in the form of sound waves having a known frequency in a system having both sound waves and a fluid traveling therethrough, comprising: a. a duct adapted to carry said fluid and said acoustic energy; b. means forming a chamber adjacent said duct separated from said duct by a wall; c. a plurality of coupling elements in said wall spaced apart a distance approximately equal to an odd multiple of one-quarter wave length of said known frequency and sized to couple a predetermined substantial portion of said acoustic energy from said duct into said chamber, said coupling elements further being sized in relationship to one another so that the energy being coupled is coupled with a high degree of directivity; and d. means associated with said chamber for disposing of the acoustic energy being coupled therein.

Claim 4

Muffler apparatus for attenuating acoustic energy in the form of sound waves having a known frequency in a system having both sound waves and a fluid traveling therethrough, comprising: a. a duct adapted to carry said fluid and said acoustic energy; b. means forming a chamber adjacent said duct separated from said duct by a wall; c. a plurality of coupling elements in said wall spaced apart a distance approximately equal to an odd multiple of one-quarter wave length of said known frequency and sized to couple a predetermined substantial portion of said acoustic energy from said duct into said chamber, said coupling elements further being sized in relationship to one another so that the energy being coupled is coupled with a high degree of directivity; and d. means associated with said chamber for disposing of the acoustic energy being coupled therein.

Claim 5

The apparatus of claim 2 wherein an inlet of said duct is connected to the exhaust outlet of an engine.

Claim 6

The apparatus of claim 2 wherein sound absorbing means are mounted in said chamber to absorb acoustic energy being coupled therein.

Claim 7

The apparatus of claim 2 wherein said chamber is formed by a second duct having an outlet opening for said acoustic energy being coupled therein and wherein means are connected to said outlet opening of said second duct to dispose of said acoustic energy being coupled therein.

Claim 8

The apparatus of claim 2 wherein said duct and chamber are formed by generally parallel first and second tubes having said coupling elements in adjoining walls thereof, said first tube having open ends to permit free flow of fluid therethrough, and said second tube having closed ends and containing an acoustic energy absorbing material.

Claim 9

The apparatus of claim 2 wherein said duct and chamber are formed by first and second generally parallel, tubular members each having opposite open ends to permit free fluid flow therethrough, wherein substantially all of the acoustic energy being coupled into the second tubular member from the first tubular member continues to travel in the same direction in the second tubular member but undergoes a phase shift of 90* during the coupling process, wherein said coupling elements are sized to couple approximately one-half of the acoustic energy from said first tubular member to said second tubular member, and further including means for conveying fluid from the fluid outlet end of said first tubular member to the adjoining end of the second tubular member for free passage of fluid through said first tubular member in one direction and through said second tubular member in the opposite direction, said acoustic energy being reflected back to its source as a result of a series of coupling actions and phase shifts between said tubular members in both directions.

Claim 10

The apparatus of claim 2 wherein said coupling elements are designed to couple substantially all of said acoustic energy into said chamber, said acoustic energy undergoing a phase shift of 90* during the coupling process, wherein a second muffler apparatus is connected to an outlet of said chamber to provide an additional phase shift of 90*, and wherein means are provided to combine the resultant sound wave shifted in phase by 180* with an equal amount of the original acoustic energy to provide cancellation thereof.

Claim 11

A muffler system, comprising: a. a first conduit adapted to carry gases and acoustic energy in the form of sound waves; b. means including second and third conduit means connected to a discharge outlet of said first conduit for dividing at least the aCoustic energy therein into two generally equal parts for separate transmission through said second and third conduit means; c. said second conduit means including directional acoustic coupling means for imposing a 180* phase shift on the sound waves being transmitted therethrough; and d. means for recombining the sound waves being discharged from said second and third conduit means to thereby reflectively cancel the oppositely phased sound waves while permitting free flow of gases therethrough.

Claim 12

A muffler system, comprising: a. a first conduit adapted to carry gases and acoustic energy in the form of sound waves; b. means including second and third conduit means connected to a discharge outlet of said first conduit for dividing at least the aCoustic energy therein into two generally equal parts for separate transmission through said second and third conduit means; c. said second conduit means including directional acoustic coupling means for imposing a 180* phase shift on the sound waves being transmitted therethrough; and d. means for recombining the sound waves being discharged from said second and third conduit means to thereby reflectively cancel the oppositely phased sound waves while permitting free flow of gases therethrough.

Claim 13

The apparatus of claim 9 wherein said second conduit means includes a pair of acoustic directional couplers, each of said couplers for imposing a 90* phase shift on the sound waves being transmitted therethrough.

Claim 14

The apparatus of claim 10 wherein each coupler comprises a first tubular member having an inlet and a second tubular member having an outlet, said members being mounted in side-by-side relationship with a wall therebetween, and wherein a plurality of coupling elements are provided in said wall to couple substantially all of the sound energy being carried by said first tubular member into said second tubular member.

Claim 15

The apparatus of claim 11 wherein said first and second tubular members are generally parallel members, and wherein said inlet and said outlet are on opposite ends of said members.

Claim 16

The apparatus of claim 10 wherein each coupler comprises a first tubular member having an inlet and a second tubular member having an outlet, said members being mounted in a side-by-side relationship with a wall therebetween, and wherein a plurality of coupling elements are provided in said wall to couple approximately one-half of the acoustic energy being carried by said first tubular member into said second tubular member.

Claim 17

The apparatus of claim 13 wherein said first and second tubular members are generally parallel members, and wherein said inlet of one member is disposed adjacent said outlet of the other member.

Claim 18

The apparatus of claim 10 wherein each coupler comprises a first tubular member and a second tubular member mounted in a side-by-side relationship with a wall therebetween, wherein a plurality of coupling elements are provided in said wall to couple acoustic energy from said first tubular member into said second tubular member, wherein an inlet of the first tubular member of the first coupler is connected to the discharge outlet of said first conduit, an outlet of said first tubular member is connected to said third conduit means, and an outlet of said second tubular member of the first coupler is connected to said second conduit means, said coupling openings of said first coupler being sized to transfer approximately one-half of the acoustic energy in said first tubular member into said second tubular member thereof, and wherein the second coupler has an inlet of the first tubular member thereof and an outlet of the second tubular member thereof connected in said second conduit means, and couples substantially all of the acoustic energy carried by the first tubular member thereof into the second tubular member thereof.

Claim 19

An engine exhaust muffler, comprising: a. a first conduit having an inlet adapted to be connected to an exhaust discharge port of an engine, and an outlet; b. a second conduit mounted in a side-by-side, generally parallel relationship with said first conduit, and having an inlet and an outlet in reverse positions with respect to said first conduit; c. conduit means connecting said outlet of said first conduit to said inlet of said second conduit to provide an exhaust flow path in one direction through said first conduit and in the opposite direction through said second conduit; d. said first and second conduits being separated by single wall means having at least a pair of coupling elements therein axially spaced apart a distance approximately equal to an odd multiple of one-quarter of the wave length of a selected frequency of sound waves emanating from the eNgine; and e. said coupling elements being sized to directionally couple approximately one-half of the sound energy over a band of frequencies centered on said selected frequency being carried by one of said conduits into the other conduit, said coupled waves being shifted by 90* to thereby reflect back to the engine substantially all of the sound energy within said frequency band emanating from said engine.

Claim 20

An engine exhaust muffler, comprising: a. a first conduit having an inlet adapted to be connected to an exhaust discharge port of an engine, and an outlet; b. a second conduit mounted in a side-by-side, generally parallel relationship with said first conduit, and having an inlet and an outlet in reverse positions with respect to said first conduit; c. conduit means connecting said outlet of said first conduit to said inlet of said second conduit to provide an exhaust flow path in one direction through said first conduit and in the opposite direction through said second conduit; d. said first and second conduits being separated by single wall means having at least a pair of coupling elements therein axially spaced apart a distance approximately equal to an odd multiple of one-quarter of the wave length of a selected frequency of sound waves emanating from the eNgine; and e. said coupling elements being sized to directionally couple approximately one-half of the sound energy over a band of frequencies centered on said selected frequency being carried by one of said conduits into the other conduit, said coupled waves being shifted by 90* to thereby reflect back to the engine substantially all of the sound energy within said frequency band emanating from said engine.

Claim 21

An engine exhaust muffler, comprising: a. a first conduit having an inlet adapted to be connected to an exhaust discharge port of an engine, and an outlet; b. a second conduit mounted in a side-by-side generally parallel relationship with said first conduit, and having one closed end, said closed end being positioned adjacent said outlet of said first conduit; c. said conduits being separated by wall means having at least a pair of coupling elements therein spaced apart axially a distance approximately equal to an odd multiple of one-quarter of the wave length of a selected frequency of sound waves emanating from the engine; and d. said coupling openings being sized to directionally couple substantially all of the sound energy being carried by one of said conduits into the other conduit to thereby reflect back to the engine substantially all of the sound energy emanating from the engine at said selected frequency.

Claim 22

An engine exhaust muffler, comprising: a. a first conduit having an inlet adapted to be connected to an exhaust discharge port of an engine, and an outlet; b. a second conduit mounted in a side-by-side generally parallel relationship with said first conduit, and having one closed end, said closed end being positioned adjacent said outlet of said first conduit; c. said conduits being separated by wall means having at least a pair of coupling elements therein spaced apart axially a distance approximately equal to an odd multiple of one-quarter of the wave length of a selected frequency of sound waves emanating from the engine; and d. said coupling openings being sized to directionally couple substantially all of the sound energy being carried by one of said conduits into the other conduit to thereby reflect back to the engine substantially all of the sound energy emanating from the engine at said selected frequency.