US3132715A - Noise reducing enclosures - Google Patents

Noise reducing enclosures Download PDF

Info

Publication number
US3132715A
US3132715A US195701A US19570162A US3132715A US 3132715 A US3132715 A US 3132715A US 195701 A US195701 A US 195701A US 19570162 A US19570162 A US 19570162A US 3132715 A US3132715 A US 3132715A
Authority
US
United States
Prior art keywords
enclosure
noise
mass
noise reducing
absorber
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US195701A
Inventor
Dunsbee John
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ferranti International PLC
Original Assignee
Ferranti PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ferranti PLC filed Critical Ferranti PLC
Application granted granted Critical
Publication of US3132715A publication Critical patent/US3132715A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/33—Arrangements for noise damping

Definitions

  • a noise reducing enclosure there is included within a noise reducing enclosure at least one resonant absorber tuned to include the objection-able frequencies of the noise source, each said absorber being positioned with its mass side facing a side of said enclosure and separated therefrom by a narrow passage.
  • the expression mass side as used herein with reference to a resonant absorber means that side of the absorber which forms or contains the acoustic mass.
  • Said passage may be freely connected to the remainder of the space within the enclosure.
  • Said absorbers may extend over the greater part of the inside surface of said enclosure.
  • FIGURE 1 is a sectional elevation of a transformer noise reducing enclosure in accordance with the invention.
  • FIGURE 2 is a sectional plan of the enclosure shown in FIGURE 1, the section being taken on the line 2-2 in FIGURE 1.
  • a transformers 1 is enclosed within a brick enclosure 2 which includes tour shallow resonant absorbers 3 tuned to resonate at a frequency of one hundred cycles per second, this being the predominant trequency of transformer noise.
  • Resonant absorbers which are well known, may be considered to consist of acoustic mass, compliance and resistance and usually comprise a Helmholtz resonator or a panel absorber.
  • a Helmholtz resonator includes a cavity having one or more holes in one side, herein referrcd to as the mass side since the acoustic mass is formed by the air contained within the holes, the compliance being formed by the space within the cavity and the resistance being formed by the surface roughness of the holes in the mass side or by absorbent material introduced within the cavity.
  • a panel absorber includes a cavity having a mass side formed by an elastic panel or mem- 3,132,715 Patented May 12, 1964 brane.
  • the acoustic mass may be formed by the mass of the membrane alone or the mass may be increased by adding additional non-clastic mass to the membrane.
  • the compliance is thespace within the cavity and the elasticity of the membrane may provide additional compliance and also resistance. Alaternatively, resistance may be formed by absorbent material introduced within the cavity. i
  • the resonant absorber 3 shown in the drawings are of the Helmholtz kind. Each resonator 3 is positioned with its-mass side facing a side of the enclosure 2 and is separated therefrom by a narrow passage 4 and is also separated from the transformer 1 by a larger space 5. The resonators 3 extend over the greater partof the inside surface of each side of the enclosure 2, a gap 6 being pro vided between the top of the resonators 3 and the top of the enclosure 2 to freely connect the passage 4 and the space 5 and thereby prevent resonance within the passage 4.
  • noise at a frequency of one hundred cycles per second emanating from the transformer -1 causes resonance in the absorbers 3.
  • the greatest reduction in noise intensity occurs just in front of the mass side of the resonators, -i.e., within the passages 4, and the sound passing through the wall of the enclosure 2 is therefore considerably reduced.
  • the noise intensity within the shallow resonators 3 is greater than the noise Within the space 5 and some sound is therefor radiated back into the enclosure through the solid sides of the resonators 3. it is therefore essential that the resonators be positioned with their mass sides facing the sides of the enclosure 2 and spaced therefrom by the narrow passage 4.
  • the resonators 3 may extend over the whole of the inside surface of each side of the enclosure 2 but if as a result of this resonance should occur in the passage 4 the reduction in sound intensity outside the enclosure may not be so great.
  • the Helmholtz resonators may be replaced by panel absorbers.
  • the absorbers may only be positioned adjacent the side of the enclosure facing in that particular direction. If a reduction in the intensity of noise passing through the top of the enclosure is also required a further resonant absorber may similarly be positioned adjacent the top of the enclosure.
  • each of the resonators 3 has been described as a single resonator, but for a large enclosure each resonator would be built up from a number of smaller units.
  • each resonator would be built up from a number of smaller units.
  • the invention has been described with reference to a transformer noise reducing enclosure it is equally suitable for noise reducing enclosures for other apparatus, such as rotating machinery, the resonant absorbers being tuned to include the objectionable trequencics of the noise emanating from the apparatus.
  • a noise reducing enclosure for a noise source having included therein at least one resonant absorber comprising a single mass side, said absorber being tuned to include the objectionable frequencies of the noise source, each said absorber being positioned with its mass side facing a side of said enclosure and separated therefrom by a narrow passage.
  • Anoise reducing enclosure as claimed in claim 1 in which said passage is treely connected to the remainder of the space within the enclosure.
  • a noise reducing enclosure as claimed in claim 1 in which a plurality of resonant absorbers are provided, said absorbers extending over the greater part of the inside surface of said enclosure.
  • a noise reducing enclosure for a noise source having included therein 'aplur-alityof resonant absorbers each comprising a single rnass side and each being tuned to include the objectionable frequencies of the noise source, each of said absorbers being positioned with its mass side facing a side of said enclosure and separated therefrom by a narrow passage which is freely connected to rthe remainder of the space Within the enclosure, said absorbers extending over the greater part of the inside surface of each side of said enclosure.

Description

y 12, 1964 J. DUNSBEE 3,132,715
NOISE REDUCING ENCLOSURES Filed May 18, 1962 6 F/ 'g./. V///// i 5 ///:Z4 ,A-s
lnvenlor J-OHN DUMSBE E y M m 9 Attorneys United States Patent 3,132,715 NOISE REDUCING ENCLOSURES John Dunsbee, Royton, England, assignor t0 Ferranti, Limited, Hollinwood, England, a company of Great Britain and Northern Ireland Filed May 18, 1962, Ser. No. 195,701 Claims priority, application Great Britain June 1, 19 61 6 Claims. (Cl. 181-33) This invention relates to noise reducing enclosures.
It is often required to minimize the noise emanating from an apparatus such as a machine or an electrical transformer and for this purpose it is known to place the apparatus in an enclosure. The reduction of noise intensity achieved by the use of a simple enclosure is a function of the mass of the enclosure and the frequency of the noise and therefore, to reduce the intensity of low frequency noise, for example a frequency of one hundred cycles per second for transformer noise, an enclosure of large mass must be provided. It has been proposed to reduce the noise intensity further by including sound absorbing material within the enclosures but at low frequencies the space required, either partially or nearly completely filled with absorbent material, to give an appreciable reduction in the noise intensity is excessive and necessitates the provision of a much larger enclosure.
It is an object of the present invention to provide a noise reducing enclosure suitable for use with low frequency noise sources or noise sources containing low frequency noise in their spectrum in which a reduction in the low frequency noise intensity is obtained without requiring an excessive increase in the size or mass of the enclosure.
According to the present invention there is included within a noise reducing enclosure at least one resonant absorber tuned to include the objection-able frequencies of the noise source, each said absorber being positioned with its mass side facing a side of said enclosure and separated therefrom by a narrow passage. The expression mass side as used herein with reference to a resonant absorber means that side of the absorber which forms or contains the acoustic mass.
Said passage may be freely connected to the remainder of the space within the enclosure.
Said absorbers may extend over the greater part of the inside surface of said enclosure.
On embodiment of the present invention will now be described by way of example with reference to the ac companying drawings in which:
FIGURE 1 is a sectional elevation of a transformer noise reducing enclosure in accordance with the invention, and
FIGURE 2 is a sectional plan of the enclosure shown in FIGURE 1, the section being taken on the line 2-2 in FIGURE 1.
Referring now to the drawings, a transformers 1 is enclosed within a brick enclosure 2 which includes tour shallow resonant absorbers 3 tuned to resonate at a frequency of one hundred cycles per second, this being the predominant trequency of transformer noise.
Resonant absorbers, which are well known, may be considered to consist of acoustic mass, compliance and resistance and usually comprise a Helmholtz resonator or a panel absorber. A Helmholtz resonator includes a cavity having one or more holes in one side, herein referrcd to as the mass side since the acoustic mass is formed by the air contained within the holes, the compliance being formed by the space within the cavity and the resistance being formed by the surface roughness of the holes in the mass side or by absorbent material introduced within the cavity. A panel absorber includes a cavity having a mass side formed by an elastic panel or mem- 3,132,715 Patented May 12, 1964 brane. The acoustic mass may be formed by the mass of the membrane alone or the mass may be increased by adding additional non-clastic mass to the membrane. The compliance is thespace within the cavity and the elasticity of the membrane may provide additional compliance and also resistance. Alaternatively, resistance may be formed by absorbent material introduced within the cavity. i
The resonant absorber 3 shown in the drawings are of the Helmholtz kind. Each resonator 3 is positioned with its-mass side facing a side of the enclosure 2 and is separated therefrom by a narrow passage 4 and is also separated from the transformer 1 by a larger space 5. The resonators 3 extend over the greater partof the inside surface of each side of the enclosure 2, a gap 6 being pro vided between the top of the resonators 3 and the top of the enclosure 2 to freely connect the passage 4 and the space 5 and thereby prevent resonance within the passage 4.
In operation, noise at a frequency of one hundred cycles per second emanating from the transformer -1 causes resonance in the absorbers 3. The greatest reduction in noise intensity occurs just in front of the mass side of the resonators, -i.e., within the passages 4, and the sound passing through the wall of the enclosure 2 is therefore considerably reduced.
The noise intensity within the shallow resonators 3 is greater than the noise Within the space 5 and some sound is therefor radiated back into the enclosure through the solid sides of the resonators 3. it is therefore essential that the resonators be positioned with their mass sides facing the sides of the enclosure 2 and spaced therefrom by the narrow passage 4.
The embodiment described above may be varied in many ways. For example, the resonators 3 may extend over the whole of the inside surface of each side of the enclosure 2 but if as a result of this resonance should occur in the passage 4 the reduction in sound intensity outside the enclosure may not be so great. Also, the Helmholtz resonators may be replaced by panel absorbers. Furthermore, if it is only required to reduce the noise in a particular direction the absorbers may only be positioned adjacent the side of the enclosure facing in that particular direction. If a reduction in the intensity of noise passing through the top of the enclosure is also required a further resonant absorber may similarly be positioned adjacent the top of the enclosure.
It will be appreciated that each of the resonators 3 has been described as a single resonator, but for a large enclosure each resonator would be built up from a number of smaller units. Furthermore, whilst the invention has been described with reference to a transformer noise reducing enclosure it is equally suitable for noise reducing enclosures for other apparatus, such as rotating machinery, the resonant absorbers being tuned to include the objectionable trequencics of the noise emanating from the apparatus.
What we claim is:
l. A noise reducing enclosure for a noise source having included therein at least one resonant absorber comprising a single mass side, said absorber being tuned to include the objectionable frequencies of the noise source, each said absorber being positioned with its mass side facing a side of said enclosure and separated therefrom by a narrow passage.
2. Anoise reducing enclosure as claimed in claim 1 in which said passage is treely connected to the remainder of the space within the enclosure.
3. A noise reducing enclosure as claimed in claim 1 in which a plurality of resonant absorbers are provided, said absorbers extending over the greater part of the inside surface of said enclosure.
4.'A noise reducing enclosure as claimed in claim 1 in which said resonant ebsorbens are Helmholtz resonators.
5. A noise reducing enclosure for a noise source having included therein 'aplur-alityof resonant absorbers each comprising a single rnass side and each being tuned to include the objectionable frequencies of the noise source, each of said absorbers being positioned with its mass side facing a side of said enclosure and separated therefrom by a narrow passage which is freely connected to rthe remainder of the space Within the enclosure, said absorbers extending over the greater part of the inside surface of each side of said enclosure.
6. A noise reducing enclosure as claimed in claim 5 in which said resonant absorbers are Helmholtz resonators.
UNITED STATES PATENTS Roos et a1 June 23, 1936 Parkinson June 1, 1937 Grutzner July 12, 1938 Olson Mar. 28, 1950 Kjaer Dec. 2, 1952 Meyers Oct. 1, 1957 FOREIGN PATENTS Great Britain Nov. 16, 1938 France Aug. 5, 1957

Claims (1)

1. A NOISE REDUCING ENCLOSURE FOR A NOISE SOURCE HAVING INCLUDED THEREIN AT LEAST ONE RESONANT ABSORBER COMPRISING A SINGLE MASS SIDE, SAID ABSORBER BEING TUNED TO INCLUDE THE OBJECTIONABLE FREQUENCIES OF THE NOISE SOURCE,
US195701A 1961-06-01 1962-05-18 Noise reducing enclosures Expired - Lifetime US3132715A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3132715X 1961-06-01

Publications (1)

Publication Number Publication Date
US3132715A true US3132715A (en) 1964-05-12

Family

ID=10922281

Family Applications (1)

Application Number Title Priority Date Filing Date
US195701A Expired - Lifetime US3132715A (en) 1961-06-01 1962-05-18 Noise reducing enclosures

Country Status (1)

Country Link
US (1) US3132715A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3967693A (en) * 1973-05-24 1976-07-06 Asahi Kasei Kogyo Kabushiki Kaisha Apparatus for dismissing or decreasing sound's energy
US4982812A (en) * 1989-10-24 1991-01-08 Hwang Min Su Noise-preventive means for compressor used in air conditioner
US20080197550A1 (en) * 2007-02-14 2008-08-21 Integrated Dynamics Engineering Gmbh Method for adapting a vibration isolation system
DE102015215454A1 (en) * 2015-08-13 2017-02-16 Siemens Aktiengesellschaft Device for damping sound with a known frequency and amplitude, cooling system and electrical system with the device

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2045312A (en) * 1933-07-20 1936-06-23 United States Gypsum Co Acoustical wall covering
US2081952A (en) * 1934-12-17 1937-06-01 Johns Manville Acoustical construction
US2123358A (en) * 1937-01-29 1938-07-12 Fairbanks Morse & Co Engine silencing hood
GB495755A (en) * 1937-03-16 1938-11-16 Abram Rupert Neelands Silencing equipment for air, heating, ventilating, and exhaust ducts, tunnels or the like, and sound treatment for rooms
US2502016A (en) * 1943-11-30 1950-03-28 Rca Corp Diffraction type sound absorber
US2619685A (en) * 1945-06-20 1952-12-02 Ind Osakeyhtio Sound absorbent sheathing for walls or ceilings
US2808122A (en) * 1955-07-20 1957-10-01 Eastman Kodak Co Construction for dampening engine noise
FR1150315A (en) * 1956-05-30 1958-01-10 Sound-absorbing coating

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2045312A (en) * 1933-07-20 1936-06-23 United States Gypsum Co Acoustical wall covering
US2081952A (en) * 1934-12-17 1937-06-01 Johns Manville Acoustical construction
US2123358A (en) * 1937-01-29 1938-07-12 Fairbanks Morse & Co Engine silencing hood
GB495755A (en) * 1937-03-16 1938-11-16 Abram Rupert Neelands Silencing equipment for air, heating, ventilating, and exhaust ducts, tunnels or the like, and sound treatment for rooms
US2502016A (en) * 1943-11-30 1950-03-28 Rca Corp Diffraction type sound absorber
US2619685A (en) * 1945-06-20 1952-12-02 Ind Osakeyhtio Sound absorbent sheathing for walls or ceilings
US2808122A (en) * 1955-07-20 1957-10-01 Eastman Kodak Co Construction for dampening engine noise
FR1150315A (en) * 1956-05-30 1958-01-10 Sound-absorbing coating

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3967693A (en) * 1973-05-24 1976-07-06 Asahi Kasei Kogyo Kabushiki Kaisha Apparatus for dismissing or decreasing sound's energy
US4982812A (en) * 1989-10-24 1991-01-08 Hwang Min Su Noise-preventive means for compressor used in air conditioner
US20080197550A1 (en) * 2007-02-14 2008-08-21 Integrated Dynamics Engineering Gmbh Method for adapting a vibration isolation system
US8170225B2 (en) * 2007-02-14 2012-05-01 Integrated Dynamics Engineering Gmbh Method for adapting a vibration isolation system
DE102015215454A1 (en) * 2015-08-13 2017-02-16 Siemens Aktiengesellschaft Device for damping sound with a known frequency and amplitude, cooling system and electrical system with the device

Similar Documents

Publication Publication Date Title
US3546504A (en) Noise reducing arrangement for electric motors
US3887031A (en) Dual-range sound absorber
US2252846A (en) Acoustic device
US3087574A (en) High acoustic transmission loss panel and the like
US10334353B2 (en) Loudspeaker module and electronic product
WO2020024522A1 (en) Sound generation apparatus and portable terminal
US3132715A (en) Noise reducing enclosures
US2917127A (en) Acoustic enclosure for loudspeakers
US2866514A (en) Corrective loud speaker enclosure
US2488555A (en) Diffraction type sound absorber with fibrous walls
US2505854A (en) Sound absorbing casing for noise emitting apparatus
US2121008A (en) Acoustic translating device
BR8101223A (en) ELECTRIC ACOUSTIC TRANSDUCER
KR840004550A (en) Head box with vibration absorber
CN106604579B (en) A kind of annular circuit board buffering vibration insulation structure
JPH0327778B2 (en)
US3075619A (en) Vibration suppressor
GB932521A (en) Improvements relating to noise reducing enclosures
US5184104A (en) Electromagnetic induction apparatus with a sound suppressing arrangement
US3319737A (en) Acoustical enclosures
US3016430A (en) Loudspeaker
US2294125A (en) Mechanical vibrating system
CN109707596B (en) Silencing device and refrigerator with same
US1908513A (en) Loud speaker
FR2417229A1 (en) Damping technique for loudspeaker, or sound-proof box - uses elastomer between transducer and enclosure and in enclosure joints to reduce resonance effects