US3920095A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Free flow sound attenuating device and method of using
Assignee: Technetics Corp
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Filing: 1974-02-01
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Granted: 1975-11-18
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Expires: 1994-02-01
Abstract
Abstract A sound attenuating device characterized by several novel structures which include (1) a foraminous conduit surrounded by (2) a housing having in series after the inlet end (3) a low frequency attenuator and (4) a high frequency attenuator, the conduit acting in operative association with the low frequency attenuator to enhance the effectiveness of the high frequency attenuator by providing a lower resistance to the high frequency sound entering the high frequency attenuator.
Inventors
- 👤 Raymond C Clark
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 05:03
CPC Classifications
F; F16; F16L; F16L55/00; F16L55/02; F16L55/033
Claims Analysis
Total Claims: 40
Claim 1
Independent Claim
122 words
A device for attenuating sound in a fluid flowing therefrom, the fluid having a known acoustical impedance measured in rayls, comprising a housing surrounding a conduit having an inlet and an outlet, the conduit having in series after the inlet: first means for attenuating low frequency sound entering the device; and second means for attenuating high frequency sound entering the device, the second means having a foraminous duct in series with said conduit, the duct having a preselected acoustical resistance measured in rayls substantially the same value in rayls as the impedance of the flowing fluid, the first means attenuating the low frequency sound to a level sufficiently low to enable the foraminous duct to effectively function at its preselected acoustical resistance.
Claim 2
Independent Claim
122 words
A device for attenuating sound in a fluid flowing therefrom, the fluid having a known acoustical impedance measured in rayls, comprising a housing surrounding a conduit having an inlet and an outlet, the conduit having in series after the inlet: first means for attenuating low frequency sound entering the device; and second means for attenuating high frequency sound entering the device, the second means having a foraminous duct in series with said conduit, the duct having a preselected acoustical resistance measured in rayls substantially the same value in rayls as the impedance of the flowing fluid, the first means attenuating the low frequency sound to a level sufficiently low to enable the foraminous duct to effectively function at its preselected acoustical resistance.
Claim 3
Dependent Claim
15 words
A device as recited in claim 1 wherein the device is a free flow device.
Claim 4
Dependent Claim
14 words
A device as recited in claim 2 wherein the fluid is a flowing gas.
Claim 5
Dependent Claim
15 words
The device as recited in claim 1 wherein the first means is a Helmholtz resonator.
Claim 6
Dependent Claim
16 words
The device as recited in claim 4 wherein the first means is tuned to 250 Hz.
Claim 7
Dependent Claim
15 words
The device as recited in claim 1 wherein the first means is a baffle system.
Claim 8
Dependent Claim
16 words
The device as recited in claim 6 wherein the baffle system is a multi-dimensional baffle system.
Claim 9
Dependent Claim
15 words
The device as recited in claim 1 wherein the first means is a retroverted system.
Claim 10
Dependent Claim
15 words
The device as recited in claim 1 wherein the first means is an expansion chamber.
Claim 11
Dependent Claim
17 words
The device as recited in claim 1 wherein the second means is a quarter-wave standing wave cavity.
Claim 12
Dependent Claim
28 words
The device as recited in claim 10 wherein the depth a of the standing wave cavity is an odd multiple of one-quarter wavelengths of the sound pressure level.
Claim 13
Dependent Claim
16 words
The device as recited in claim 11 wherein the second means is tuned above 1000 Hz.
Claim 14
Dependent Claim
21 words
The device as recited in claim 1 wherein the foraminous duct has an effective impedance in the range 3-30 cgs rayls.
Claim 15
Dependent Claim
21 words
The device as recited in claim 1 wherein the foraminous duct has an effective impedance in the range 31-100 cgs rayls.
Claim 16
Dependent Claim
21 words
The device as recited in claim 1 wherein the foraminous duct has an effective impedance in the range 101-400 cgs rayls.
Claim 17
Dependent Claim
16 words
The device as recited in claim 1 wherein the foraminous duct is a laminated screen structure.
Claim 18
Dependent Claim
15 words
The device as recited in claim 1 wherein the foraminous duct is a perforated tube.
Claim 19
Dependent Claim
19 words
The device of claim 17 wherein the perforated tube is made of metal with metal fiber in the openings.
Claim 20
Dependent Claim
17 words
The device as recited in claim 1 wherein the foraminous duct is a metal fiber web structure.
Claim 21
Dependent Claim
28 words
The device as recited in claim 19 wherein the metal fiber web structure has the inside surface thereof covered with a layer of fibers having a protective coating.
Claim 22
Dependent Claim
14 words
The device as recited in claim 20 wherein the fibers are made of metal.
Claim 23
Dependent Claim
14 words
The device as recited in claim 20 wherEin the fibers are of organic material.
Claim 24
Dependent Claim
14 words
The device as recited in claim 20 wherein the fibers are of ceramic material..
Claim 25
Dependent Claim
15 words
The device as recited in claim 20 wherein the protective coating is an oxidation catalyst.
Claim 26
Dependent Claim
26 words
The device as recited in claim 1 further including third means, located in series after the second means, for attenuating middle frequency sound entering the device.
Claim 27
Dependent Claim
15 words
The device as recited in claim 25 wherein the third means is a Helmholtz resonator.
Claim 28
Dependent Claim
21 words
The device as recited in claim 25 wherein the third means is tuned within the range 500 Hz to 1000 Hz.
Claim 29
Dependent Claim
66 words
The device as recited in claim 1 further including in series after the second means, a plurality of quarter-wave standing wave cavities surrounding a portion of the periphery of the foraminous duct; at least one Helmholtz resonator surrounding the plurality of standing wave cavities and communicating with the foraminous duct by ports located in the conduit at those portions not communicating with the standing wave cavities.
Claim 30
Dependent Claim
19 words
The device as recited in claim 1 wherein the foraminous duct comprises two foraminous tubes parallel to each other.
Claim 31
Dependent Claim
13 words
The device of claim 1 wherein the second means is a laminar absorber.
Claim 32
Independent Claim
98 words
A method for attenuating the level of sound in a fluid flowing through a muffler, the fluid having a known acoustical impedance measured in rayls, comprising the steps of: a. providing a high frequency sound attenuator for absorbing frequencies over 1000 Hz, the attenuator having an acoustical resistance in rayls matched to the acoustical impedance of a fluid entering the muffler; and b. providing a low frequency sound attenuator to absorb sound having a frequency of under 1000 Hz to a level sufficiently low to enable the high frequency attenuator to effectively function at its preselected acoustical resistance.
Claim 33
Independent Claim
98 words
A method for attenuating the level of sound in a fluid flowing through a muffler, the fluid having a known acoustical impedance measured in rayls, comprising the steps of: a. providing a high frequency sound attenuator for absorbing frequencies over 1000 Hz, the attenuator having an acoustical resistance in rayls matched to the acoustical impedance of a fluid entering the muffler; and b. providing a low frequency sound attenuator to absorb sound having a frequency of under 1000 Hz to a level sufficiently low to enable the high frequency attenuator to effectively function at its preselected acoustical resistance.
Claim 34
Dependent Claim
16 words
The method as recited in claim 31 wherein the low frequency attenuator is a Helmholz resonator.
Claim 35
Dependent Claim
14 words
The method of claim 30 wherein the high frequency attenuator is a foraminous tube.
Claim 36
Dependent Claim
15 words
The method of claim 33 wherein the foraminous tube is a mesh of metal fibers.
Claim 37
Dependent Claim
14 words
The method of claim 33 wherein the tube is a woven metal fiber tube.
Claim 38
Dependent Claim
28 words
The method of claim 35 wherein the woven metal fiber tube has the inside surface thereof covered with a layer of metal fibers coated with an oxidation catalyst.
Claim 39
Dependent Claim
19 words
The method as recited in claim 30 wherein the high frequency attenuator includes a quarter wave standing wave cavity.
Claim 40
Dependent Claim
26 words
The method of claim 37 wherein the depth a of the standing wave cavity is an odd multiple of onequarter wavelengths of the sound pressure level.
References Cited (Backward Citations)
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US3113635A
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US3362783A
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US3690606A
Cited
US3734234A
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US3831710A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-17 | 1979-05-19 | 1979-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-17 | 1983-05-19 | 1983-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-17 | 1987-05-19 | 1987-11-18 | $7700.00 | Window Closed / Lapsed |