US3812931A - Sound barrier - Google Patents

Sound barrier Download PDF

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Publication number
US3812931A
US3812931A US00300108A US30010872A US3812931A US 3812931 A US3812931 A US 3812931A US 00300108 A US00300108 A US 00300108A US 30010872 A US30010872 A US 30010872A US 3812931 A US3812931 A US 3812931A
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United States
Prior art keywords
chambers
area
traffic area
sound
openings
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Expired - Lifetime
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US00300108A
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English (en)
Inventor
J Hauskins
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ENG OF AMERICA CORP
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ENG OF AMERICA CORP
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Priority to US00300108A priority Critical patent/US3812931A/en
Priority to JP8890073A priority patent/JPS5321211B2/ja
Priority to DE19732353298 priority patent/DE2353298A1/de
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Publication of US3812931A publication Critical patent/US3812931A/en
Anticipated expiration legal-status Critical
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    • 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
    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01F—ADDITIONAL WORK, SUCH AS EQUIPPING ROADS OR THE CONSTRUCTION OF PLATFORMS, HELICOPTER LANDING STAGES, SIGNS, SNOW FENCES, OR THE LIKE
    • E01F8/00—Arrangements for absorbing or reflecting air-transmitted noise from road or railway traffic
    • E01F8/0005—Arrangements for absorbing or reflecting air-transmitted noise from road or railway traffic used in a wall type arrangement
    • E01F8/0047—Arrangements for absorbing or reflecting air-transmitted noise from road or railway traffic used in a wall type arrangement with open cavities, e.g. for covering sunken roads
    • E01F8/0052—Grate-style, e.g. as wall facing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N1/00—Silencing apparatus characterised by method of silencing
    • F01N1/02—Silencing apparatus characterised by method of silencing by using resonance

Definitions

  • a sound barrier for attenuating noise emanating from a traffic area such as a freeway.
  • the barrier borders the traffic area and incorporates a plurality of spaced-apart Helmholtz chambers, each comprising an elongated chamber having openings therein.
  • the chambers may be of triangular cross section with an edge formed by the apex of the triangular cross section facing toward the traffic area.
  • the openings are positioned in the sides of the triangular chambers; the chambers are positioned so that opposing sides of adjacent chambers form inverse-acting acoustic horns focusing the sound energy from the traffic area toward the openings.
  • the openings also act as side-branch filters to assist in the attenuation of the noise.
  • the present invention pertains to sound barriers, and more particularly, to barriers for use in attenuating noise generated in a traffic area.
  • FIG. 1 is a schematic diagram useful in explianing acoustic effects on simple barriers.
  • FIGS. 2a and 2b are schematic drawings of simple theoretical Helmholtz resonators.
  • FIG. 3 is a persepective view, partly broken away, of a Helmholtz chamber constructed for use in the sound barrier of the present invention.
  • FIG. 4 is a pictorial illustration of a sound barrier constructed in accordance with the. teachings of the present invention and placed between a typical traffic area and an adjacent area.
  • FIG. 5 is across-sectional view of a plurality of chambers as used in the sound barrier of the present invention.
  • FIG. 6 is a schematic diagram useful in describing the operation of an acoustic sidebranch. 1
  • FIG. 7 is a schematic diagram useful in explaining the optical properties of the sound barrier of the present invention.
  • a possible approach to shield traffic area noise from adjacent areas is the utilization of a simple wall or plate.
  • Barriers consisting of a plate" having elastic properties and known thickness affect a sound field in two ways:
  • FIG. I shows the action of these influences on a typical sound wave striking a barrier.
  • the objective in barrier design is to keep the sum of L'" and L as small as possible with respect to L This objective can be achieved with only limited success using conventional earthworkv or solid upright barriers.
  • the effective wavelength of trafficnoise is about 2 to 3 feet (300 500 Hz).
  • automobile noise sources are located on or near the road surface, while truck noise sources are effectively between the road surface and the exhaust exit.
  • reflected noise serves to increase the amplitude of the sound waves traversing the top of the opposite wall. This applies in the case where a barrier is emplaced on both sides of the roadway. The actual noise levels impinging on the barrier surfaces undoubtedly exceed those derived from the empirical models for a given traffic flow pattern. The reader can observe this phenomenon for himself by observing the increase in apparent road noise as his vehicle enters a section of depressed roadway. The reflected sound components from the walls simply reinforce the noise generated at a discrete moment in time. The reflected noise component is partially dissipated in the traffic corridor between the barrier walls (much to the annoyance of the motorist) and partially amplifies the component of diffracted noise over the barrier.
  • Helmholtz resonating chambers are integral to the design of the screen; by varying the length of the cavity opening it is possible to tune the resonator to any selected frequency. Inverseacting acoustic horns focus the sound energy toward the openings of the Helmholtz resonators, thus greatly increasing their efficiency.
  • the cavity openings of the Helmholtz chambers act as side-branch filters for the incident sound waves, adding to the dampening effect on the transmitted component of the sound wave.
  • the simple Helmholtz resonator may be discussed in terms of its analogous mechanical counterpart, the damped spring oscillator.
  • the simple Helmholtz resonator shown in FIG. 2a as consisting of a rigid enclosure of volume V, connected to the external air mass through a small opening of radius a and length L.
  • the gas in the cavity opening corresponds to the spring in the mechanical system and may be considered to move in and out as a unit under fluctuating pressure from the external air.
  • the pressure of the air inside the cavity changes as it is alternately compressed and expanded due to movement of the air in the neck, and this corresponds to the stiffness element of the mechanical analog.
  • L L 2AL L l6a/31r L L 2AL L l6a/31r.
  • the length of the opening is negligible and a resonator having the configuration shown in FIG. 2! will also have a definite effective length and volume.
  • the resonance frequency of the Helmholtz chamber occurs at the frequency too when the acoustic reactancc equals zero. That is, the energy impinging on the resonator is radiated back to the external medium exactly in phase except for some viscous energy losses at the neck due to the large increase in the amplitude component under these conditions.
  • the resonant frequency for a given Helmholtz chamber can be expressed by the formula woM l/woC 0 where:
  • the shape of the resonator chamber is not a factor in determining the resonant frequency of a Helmholtz chamber. For a given opening, it is the volume of the cavity, not its shape that is important. In fact, as long as the linear dimensions of the cavity are considerably less than a quarter wavelength and the opening is not too large, the resonant frequencies of cavities having the same opening but very different shapes are found to be identical.
  • Helmholtz resonators have additional resonant frequencies which are higher than the fundamental frequency me. These frequencies result from. patterns of standing waves in the cavity rather I than the oscillating mass of air at the orifice. Consequently, the overtone frequencies depend on the shape of the cavity, rather than on its volume. This attribute may be of significance in later studies when an attempt is made to increase the frequency range over which damping occurs.
  • the increase in amplitude at the resonant frequency is denoted by the quality factor
  • Helmholtz resonators assumes that the interior cavity is linked to the outside air mass through only one orifice; however, multiple orifices are utilized on both sides of the resonator cavity in the barrier of the present invention. It can be domonstrated that the symmetrically placed orifices effectively provide the same wavelength of incident sound at which resonance occurs.
  • the barrier shown generally at 10 includes a plurality of Helmholtz chambers 12, each comprising a chamber having a constant cross section with an essentially triangular exterior.
  • the chambers incorporate openings or throat areas 15, the numbers and sizes of which are determined in accordance with the frequency range of greatest significance; those frequencies in the 500 Hz. range are considered to be the most appropriate for traffic areas such as highways.
  • the chambers 12 may be secured in place in any convenient manner, such as channel members 16 and 17 positioned on top of and below the respective chambers; the channel members may be secured in any convenient manner to the chambers to form a unitary structure or barrier.
  • the chambers 12 are Helmholtz chambers having an edge 30 formed by the apex of the essentially triangular exterior of cross section; the edge 20 points in the direction of the traffic area, i.e., points to the direction from which the noise is emanating.
  • the barrier 10 is positioned to border the traffic area indicated generally at 25 and to separate the traffic area 25 from an adjacent area 26.
  • the sides 29, 30, and 31 of the chamber extend vertically between the channels 16 and 17 with the openings 15 passing from the exterior of the chamber to the interior thereof through sides 29 and 30.
  • the side 31 is positioned facing the adjacent area 26; adjacent chambers are spaced from each other to provide certain optical characteristics to be described more fully hereinafter.
  • the sides 29 and 30 of the respective Helmholtz chambers form inverse-acting acoustic horns with the adjacent sides of the adjacent chambers. These sides 29 and 30 may be approximately 2 /2 inches wide, thus rendering a cross section with a triangular outline that provides a wide angle inverse acoustic horn between adjacent chambers.
  • the openings act as side-branch filters for the incident sound waves emanating from the traffic area 25.
  • the dimensions of the Helmholtz chambers 12 may vary and the materials utilized in their construction may be chosen from a wide selection, the characteristics of which may contribute to the effectiveness of the chambers.
  • one embodiment incorporates extruded aluminum chambers 12 having a height of 3', four such chambers being stacked to present a total height between channels 16 and 17 of approximately 12, while the side 31 ofeach channel is approximately 3 inches wide. Channels with these dimensions have been placed with Va inch spaces or apertures therebetween.
  • openings 15 are chosen with the attenuation frequency range in mind; in the embodiment described here, these openings are approximately 6 inches in length and 0.15 inch wide; twelve of such openings are placed in each of the sides 29 and 30.
  • the barrier of the present invention uses the exterior walls of the wedge-shaped Helmholtz chambers as a multiple inverse acoustic horn.
  • the acoustic horn is essentially a transformer, acting more efficiently than the oscillating mass alone because the horn creates a better impedance match between the oscillating element and the external air.
  • the net result of this air coupling" effect is to maximize viscous energy losses for sound waves entering the Helmholtz chamber.
  • FIG. 5 To analyze the pressure amplification function of the acoustic horn in the barrier of the present invention, refer to FIG. 5, wherein a plane wavefront 40 may be seen impinging on the air column at the mouth of the horn. There will be some scattering of energy as the wave enters the constricting area 40 just inside the mouth, but if another wavefront enters the mouth before the first has an opportunity to dissipate, then the first wave will be forced into an area of increasing pres sure until it reaches the opening 43 of the Helmholtz chamber 44.
  • the acoustic efficiency of a horn at a given frequency is related to its shape; that is, horns with long air columns and slowly expanding walls transmit low frequencies best, while high frequencies are best transmitted in horns with quickly flaring sides and shorter air columns.
  • the acoustic horn used in the barrier of the present invention possesses a mouth 50 sufficiently broad to capture the lower frequency sound waves of interest, an air column length 51 which will pennit two or more sound pressure fronts to be present in the horn simultaneously, and an inefficient mouth-air column relationship so that radiated sound from the Helmholtz chamber is returned to the surrounding air with minimum amplification.
  • the barrier of the present invention utilizes the openings 15 (FIG. 3) as acoustic side-branches to absorb sound energy from the incident sound waves.
  • FIG. 6 A simple side-branch in acoustics is illustrated in FIG. 6, where:
  • Sound energy traveling through the sound barrier of the present invention can be considered. as traveling through a short pipe of varying cross section, with the Helmholtz resonators acting as branches off the pipe.
  • Lord Rayleigh, in his Theory of Sound, Vol. ll (Dover Publications, New York 1945]) determined that resonant absorbers behaving as branches of a pipe cause strong selective absorption of sound energy.
  • the Helmholtz resonator is considered as the branch, with sound energy proceeding from the mouth of the acoustic horn pipe across the neck of the resonator (branch) and then transmitted through an aperture in the screen, the analogy for the present application is clear.
  • A the area of the resonator cavity orifice
  • R the characteristic acoustic resistance of the resonator
  • X the acoustic reactance of the resonator
  • ratio of power dissipated in reflected wave to that of incident wave a ratio of power dissipated in transmitted wave to that of incident wave.
  • the subject sound barrier may be considered a series of wedges separated by thin apertures.
  • the observer sees only a narrow angle of view through each aperture, denoted by the angle (1), which is a function of the width of the aperture, 41,, and the distance from the aperture to the observer D.
  • Ax an incremental displacement of the observer along the line of travel Ax (x x, Ax) will have a corresponding effect on the displacement of the angle of view beyond the aperture, which can be denoted as A0.
  • changes in position with time can be expressed as dx/dt K(d0/dt) where K is some constant of proportionality related to the distance D.
  • the term dx/dt is simply the velocity vector along the observers path, which in this case equals the average speed of a passing motorist.
  • the total light energy impinging on the eye of the observer from the direction of the object behind the screen is made up of the following components:
  • direct component of light from source i.e., sunlight
  • E component of direct light reflected back to observer from front face of sound screen E light reflected from object in direction of ob- I server
  • E component of reflect light from object which is re-reflected from back of sound screen T optical transmission factor of the screen.
  • a sound barrier for attenuating noise generated in a traffic area and transmitted to an adjacent area comprising: a screen bordering said traffic area and positioned between said trafiic area and said adjacent area; said screen including a plurality of vertically extending enclosed chambers each having openings therein to form resonating chambers, and including means for focusing sound energy from said traffic area into said openings; said chambers horizontally separated by optic apertures to present a full view of objects in said adjacent area to moving observers in said traffic area.
  • each of said chambers is a Helmholtz chamber.
  • a sound barrier for attenuating noise generated in a traffic area and transmitted to an adjacent area comprising: a screen bordering said traffic area and positioned between said traffic area and said adjacent area; said screen including a plurality of vertically extending Helmholtz chambers each having a constant crosssectional area; each of said chambers including two openings therein, each opening positioned to receive focused sound energy existing between said one of said chambers and an adjacent chamber; said chambers positioned at spaced intervals to intercept and attenuate sound waves emanating from said traffic area.

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  • Engineering & Computer Science (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Devices Affording Protection Of Roads Or Walls For Sound Insulation (AREA)
  • Building Environments (AREA)
US00300108A 1972-10-24 1972-10-24 Sound barrier Expired - Lifetime US3812931A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US00300108A US3812931A (en) 1972-10-24 1972-10-24 Sound barrier
JP8890073A JPS5321211B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1972-10-24 1973-08-09
DE19732353298 DE2353298A1 (de) 1972-10-24 1973-10-24 Laermbarriere

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US00300108A US3812931A (en) 1972-10-24 1972-10-24 Sound barrier

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JP (1) JPS5321211B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DE (1) DE2353298A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3936035A (en) * 1973-04-06 1976-02-03 Ake John Hugo Conrad Weimar Sound damping curtain wall
US3966015A (en) * 1975-02-19 1976-06-29 General Motors Corporation Silencer element
US4015682A (en) * 1974-01-17 1977-04-05 Alfred Keller Protecting system for roadway adjacent areas
US4050538A (en) * 1975-06-05 1977-09-27 Societe D'etudes Generales De Communications Industrielles Et Civiles-Segic Noise reducing screen
US4069768A (en) * 1975-05-28 1978-01-24 Bridgestone Tire Company Limited Device for controlling a propagation direction of noise
FR2370825A1 (fr) * 1976-11-16 1978-06-09 Lockheed Corp Barriere acoustique
US4095669A (en) * 1977-02-10 1978-06-20 Bond Sr William R Sound barrier
WO1985002640A1 (en) * 1983-12-12 1985-06-20 Lockheed Corporation Sound barrier
GB2264316A (en) * 1992-02-14 1993-08-25 Boral Edenhall Concrete Produc Noise barrier
US5469932A (en) * 1994-06-09 1995-11-28 Mcnair; Edward P. Sound barrier with oblique surfaces
US5730548A (en) * 1994-02-11 1998-03-24 Autostrade-Concessioni E Costruzioni Autostrade S.P.A. Deadening road pavement and method for its realization
US5872853A (en) * 1993-12-10 1999-02-16 Marquiss; Stanley Lynn Noise abatement device
US6371240B1 (en) * 2000-03-18 2002-04-16 Austin Acoustic Systems, Inc. Anechoic chamber
WO2007081282A1 (en) * 2006-01-16 2007-07-19 Lindberg Bjoern Noise absorbing railing
US20100243369A1 (en) * 2009-03-31 2010-09-30 Nuform Building Technologies Inc. Highway noise barrier
US8789652B2 (en) 2009-02-06 2014-07-29 Sonobex Limited Attenuators, arrangements of attenuators, acoustic barriers and methods for constructing acoustic barriers
US20160356036A1 (en) * 2015-06-03 2016-12-08 Epic Metals Corporation Tunable Specular Acoustic Deck
US9607600B2 (en) 2009-02-06 2017-03-28 Sonobex Limited Attenuators, arrangements of attenuators, acoustic barriers and methods for constructing acoustic barriers
USD829350S1 (en) * 2015-03-20 2018-09-25 Sonobex Limited Anti-sound barriers
CN115198672A (zh) * 2022-07-05 2022-10-18 交通运输部公路科学研究所 低频降噪增强型消声装置及具有该消声结构的声屏障
US11555280B2 (en) * 2020-09-29 2023-01-17 Toyota Motor Engineering & Manufacturing North America, Inc. Sound absorbing structure having one or more acoustic scatterers for improved sound transmission loss

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3382947A (en) * 1967-06-06 1968-05-14 Millard R. Biggs Acoustical control device

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3382947A (en) * 1967-06-06 1968-05-14 Millard R. Biggs Acoustical control device

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3936035A (en) * 1973-04-06 1976-02-03 Ake John Hugo Conrad Weimar Sound damping curtain wall
US4015682A (en) * 1974-01-17 1977-04-05 Alfred Keller Protecting system for roadway adjacent areas
US3966015A (en) * 1975-02-19 1976-06-29 General Motors Corporation Silencer element
US4069768A (en) * 1975-05-28 1978-01-24 Bridgestone Tire Company Limited Device for controlling a propagation direction of noise
US4050538A (en) * 1975-06-05 1977-09-27 Societe D'etudes Generales De Communications Industrielles Et Civiles-Segic Noise reducing screen
FR2370825A1 (fr) * 1976-11-16 1978-06-09 Lockheed Corp Barriere acoustique
US4095669A (en) * 1977-02-10 1978-06-20 Bond Sr William R Sound barrier
WO1985002640A1 (en) * 1983-12-12 1985-06-20 Lockheed Corporation Sound barrier
GB2264316A (en) * 1992-02-14 1993-08-25 Boral Edenhall Concrete Produc Noise barrier
US5872853A (en) * 1993-12-10 1999-02-16 Marquiss; Stanley Lynn Noise abatement device
US5730548A (en) * 1994-02-11 1998-03-24 Autostrade-Concessioni E Costruzioni Autostrade S.P.A. Deadening road pavement and method for its realization
US5469932A (en) * 1994-06-09 1995-11-28 Mcnair; Edward P. Sound barrier with oblique surfaces
US6371240B1 (en) * 2000-03-18 2002-04-16 Austin Acoustic Systems, Inc. Anechoic chamber
WO2007081282A1 (en) * 2006-01-16 2007-07-19 Lindberg Bjoern Noise absorbing railing
US8789652B2 (en) 2009-02-06 2014-07-29 Sonobex Limited Attenuators, arrangements of attenuators, acoustic barriers and methods for constructing acoustic barriers
US9607600B2 (en) 2009-02-06 2017-03-28 Sonobex Limited Attenuators, arrangements of attenuators, acoustic barriers and methods for constructing acoustic barriers
US20100243369A1 (en) * 2009-03-31 2010-09-30 Nuform Building Technologies Inc. Highway noise barrier
USD829350S1 (en) * 2015-03-20 2018-09-25 Sonobex Limited Anti-sound barriers
US20160356036A1 (en) * 2015-06-03 2016-12-08 Epic Metals Corporation Tunable Specular Acoustic Deck
US9932736B2 (en) * 2015-06-03 2018-04-03 Epic Metals Corporation Tunable specular acoustic deck
US11555280B2 (en) * 2020-09-29 2023-01-17 Toyota Motor Engineering & Manufacturing North America, Inc. Sound absorbing structure having one or more acoustic scatterers for improved sound transmission loss
CN115198672A (zh) * 2022-07-05 2022-10-18 交通运输部公路科学研究所 低频降噪增强型消声装置及具有该消声结构的声屏障
CN115198672B (zh) * 2022-07-05 2023-11-24 交通运输部公路科学研究所 低频降噪增强型消声装置及具有该消声结构的声屏障

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Publication number Publication date
DE2353298A1 (de) 1974-05-02
JPS4987127A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1974-08-21
JPS5321211B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1978-07-01

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