EP0255473A1 - Method for manufacturing a sound-absorbing element - Google Patents

Method for manufacturing a sound-absorbing element Download PDF

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Publication number
EP0255473A1
EP0255473A1 EP87810287A EP87810287A EP0255473A1 EP 0255473 A1 EP0255473 A1 EP 0255473A1 EP 87810287 A EP87810287 A EP 87810287A EP 87810287 A EP87810287 A EP 87810287A EP 0255473 A1 EP0255473 A1 EP 0255473A1
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EP
European Patent Office
Prior art keywords
constant
component
resonance
protuberances
sound
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EP87810287A
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German (de)
French (fr)
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EP0255473B1 (en
Inventor
Alfred Schneider
Hans Rudolf Tschudi
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Matec Holding AG
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Matec Holding AG
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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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B1/00—Engines characterised by fuel-air mixture compression
    • F02B1/02—Engines characterised by fuel-air mixture compression with positive ignition
    • F02B1/04—Engines characterised by fuel-air mixture compression with positive ignition with fuel-air mixture admission into cylinder
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24479—Structurally defined web or sheet [e.g., overall dimension, etc.] including variation in thickness
    • Y10T428/24521—Structurally defined web or sheet [e.g., overall dimension, etc.] including variation in thickness with component conforming to contour of nonplanar surface
    • Y10T428/24537—Parallel ribs and/or grooves
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24479—Structurally defined web or sheet [e.g., overall dimension, etc.] including variation in thickness
    • Y10T428/2457—Parallel ribs and/or grooves
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24479—Structurally defined web or sheet [e.g., overall dimension, etc.] including variation in thickness
    • Y10T428/24612—Composite web or sheet
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24628—Nonplanar uniform thickness material
    • Y10T428/24661—Forming, or cooperating to form cells

Definitions

  • the present invention relates to a method for producing an airborne sound-absorbing component which has a plurality of cup-shaped protuberances, the surfaces of which are excited to vibrate by impinging sound energy, the sound energy being at least partially absorbed and converted into heat, and a component and produced by this method a preferred use of this component
  • Components of the type described are usually made from a plastic film. They have a dense surface, a low mass and are resistant to most acids, oils, solvents as well as to relatively high temperatures and are therefore preferably used for the absorption of airborne noise in noisy workshops and for lining the housing of noise sources, especially internal combustion engines.
  • the best known embodiments of such components can be assigned to one of two different groups.
  • one group DE-OS 27 58 041
  • the rear openings ie the openings of the protuberances facing away from the incident sound field
  • the rear openings of the protuberances are closed so that the mass of the vibrating cover surface with the enclosed air forms a physical mass-spring system with a clear resonance frequency.
  • CH 626 936 the rear openings of the protuberances are not closed.
  • the components of both groups are preferably arranged in front of and at a distance from a sound-reflecting wall.
  • the resonance frequency of the cover or resonance surface depends on the shape, size and mass of this surface, on the height of the protuberance and on the mechanical loss factor and the modulus of elasticity of the used material is dependent. Practical experience has confirmed that even relatively small differences in the dimensions of the protuberances severely impair the course of both the sound absorption depending on the frequency of the incident sound and the strength of the sound absorption. Despite these findings, no method for producing such components is known to date which enables the shape and dimensions of the resonance surfaces to be optimized for a given use, taking into account the material properties.
  • the maximum permissible height of the protuberances is often predetermined by the shape and dimensions of the sound source or its cladding and is usually smaller than in the known embodiments mentioned above.
  • the present invention was therefore based on the object of creating a method which enables the production of airborne sound-absorbing components which have optimum absorption properties as a function of the permissible height of the protuberances.
  • FIGS 1a and 1b are not drawn to scale for clarity.
  • the airborne sound absorbing component shown in FIGS. 1a and 1b contains a base area 10, the peripheral edge of which is provided with a stabilizing frame 11.
  • the base area has a plurality of similar truncated pyramidal protuberances, of which simply the protuberance 12 is simply identified by a reference symbol.
  • Each protuberance contains four lateral surfaces 13, 14, 15 and 16 and a cover surface 17.
  • the sizes of the protuberances which are important for the present invention are their height h and the thickness d and the size A of the cover surface which acts as the determining resonance surface. Sound absorption measurements have shown that the horizontal distance between adjacent protuberances and the angle of inclination of the side walls to the base surface have little influence on the course of the sound absorption coefficient depending on the frequency.
  • the protuberances are therefore preferably as close to one another and the side walls are designed to be as slightly inclined as the manufacturing process and practical requirements allow.
  • a plastic film can simply be thermoformed to produce the component. However, it is also possible to manufacture the component in plastic injection molding or to glue or weld protuberances formed from individual sub-areas connected to one another on a carrier film.
  • Suitable plastics are, for example, polyvinyl chloride, polyethylene, polypropylene, acrylonitrile-butadiene-styrene polymer or polycarbonate, which can be used both in compact and in foamed form. Except Due to the fact that the choice of a plastic that is best suited for a given purpose as well as its processing are within the range of expert knowledge, a detailed description of the usable materials and their processing is expressly omitted.
  • the optimal thickness d of the resonance surface becomes smaller as the height h of the protuberance increases.
  • the curves confirm that the thickness d of the resonance surface is within the range of the height h of the protuberance which is important for the practical use of the component, i.e. between 10 and 35 mm is most dependent on this height.
  • the optimal size A of the resonance surface is approximately proportional to the resonance surface thickness d.
  • Curve 30 shows the typical course of the sound level as a function of the frequency for an internal combustion engine (four-stroke gasoline engine) with four cylinders and at idle at about 800 revolutions / minute. It goes without saying that the exact course of this curve is determined not only by the type of engine mentioned, the number of revolutions and the load, but also by specific design features, the operating temperature and other parameters. However, measurements on different motors under different operating conditions have shown that the curve 30 corresponds to an average value. Curve 30 shows that the sound level is low at frequencies up to 1000 Hz, increases with increasing frequencies, reaches the maximum value at 1600 Hz, slowly decreases until around 2500 Hz and rapidly decreases at even higher frequencies.
  • FIG. 4 shows the strength of the sound absorption as a function of the frequency of the incident sound for three different embodiments of airborne sound absorbing components. All three components have truncated pyramid-shaped protuberances on the back, as in the 1a and 1b is shown. In all three embodiments, the plastic foils were deep-drawn in such a way that the side surfaces are inclined by approximately 20 ° with respect to the vertical and the protuberances are 5 mm apart in the plane of the base surface.
  • the height of the protuberances and the size of the resonance surfaces are the same for all three embodiments and are 30 mm and 35 cm2. In these embodiments, the resonance surfaces are rectangular and have an aspect ratio of approximately 0.8: 1.
  • Curve 41 shows the sound absorption of a component made of foamed polyethylene, in which the thickness of the resonance surface is 1.5 mm. This curve rises evenly from values of low sound absorption at low frequencies to a maximum sound absorption corresponding to ⁇ s ⁇ 0.8 at 1000 Hz, then drops only slightly up to frequencies of around 1250 Hz and then drops steeply to ⁇ s up to around 1500 hz ⁇ 0.3.
  • Curve 42 shows the sound absorption of a component made of compact PVC, in which the thickness of the resonance surface is 0.15 mm.
  • the curve begins at higher frequencies than curve 41, rises steeply and reaches a relatively narrow maximum value of ⁇ s ⁇ 0.9 for a frequency of 1000 Hz and then drops steeply again until ⁇ s ⁇ 0.45 at 1500 Hz.
  • Curve 43 shows the sound absorption of a component made of foamed polypropylene, in which the thickness of the resonance surfaces is 3 mm. This curve rises to frequencies zen of approximately 1250 Hz similar to curve 41, but then continues to rise to a maximum value of more than 0.95 in the frequency range around 1500 Hz and then falls more flatly than curves 41 and 42 and reaches a value of ⁇ s ⁇ 0.5 at a frequency of 4000 Hz.
  • the method according to the invention and a component produced using this method can be adapted to special working conditions or uses. It has already been mentioned that instead of the films used for the exemplary embodiments described, other plastic films with similar properties can also be used. It is also possible to design the component differently than the simple plastic film provided with protuberances. For certain uses, it may be advantageous to cover the back of the component with a porous, sound-absorbing material or to insert or put a "cover” of such material in or on the rear openings of the protuberances. It is also possible to produce a combined component with two components of the type described. Of the simple components used for this, one is to be provided with protuberances that are somewhat higher and whose base area is somewhat larger than the other.
  • protuberances enables the components to be placed on one another in such a way that only the webs of the base surfaces arranged between the protuberances lie one on top of the other. Then the overlapping protuberances form a closed and a rearwardly open resonance space, with which the sound absorption and its frequency range can be further improved or expanded. Finally, it is also possible to produce a combined component from more than two components.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Vehicle Interior And Exterior Ornaments, Soundproofing, And Insulation (AREA)
  • Laminated Bodies (AREA)
  • Building Environments (AREA)
  • Transducers For Ultrasonic Waves (AREA)

Abstract

Das Verfahren ermöglicht, für schallabsorbierende Bauelemente aus kompaktem oder geschäumtem Kunststoff mit becherförmigen Ausstülpungen (12) die für eine optimale Schallabsorption erforderliche Dicke (d) und Flächengrösse (A) der Resonanzflächen in Abhängigkeit von der Höhe (h) der Ausstülpungen under der angestrebten Resonanzfrequenz zu bestimmen. Die Anwendung dieses Verfahrens ermöglicht weiter, den Frequenzverlauf des Schallabsorptionskoeffizienten des Bauelements an den Frequenzverlauf des Schallpegels einer Lärmquelle anzupassen.The method enables, for sound-absorbing components made of compact or foamed plastic with cup-shaped protuberances (12), the thickness (d) and surface area (A) of the resonance surfaces required for optimal sound absorption depending on the height (h) of the protuberances and the desired resonance frequency determine. The use of this method also makes it possible to adapt the frequency profile of the sound absorption coefficient of the component to the frequency profile of the sound level of a noise source.

Description

Die vorliegende Erfindung betrifft ein Verfahren zum Her­stellen eines Luftschall absorbierenden Bauelements, das ei­ne Mehrzahl becherförmige Ausstülpungen aufweist, deren Oberflächen von auftreffender Schallenergie zu Schwingungen angeregt werden, wobei die Schallenergie mindestens teilwei­se absorbiert und in Wärme umgewandelt wird, sowie ein nach diesem Verfahren hergestelltes Bauelement und eine bevorzug­te Verwendung dieses BauelementsThe present invention relates to a method for producing an airborne sound-absorbing component which has a plurality of cup-shaped protuberances, the surfaces of which are excited to vibrate by impinging sound energy, the sound energy being at least partially absorbed and converted into heat, and a component and produced by this method a preferred use of this component

Bauelemente der beschriebenen Art werden gewöhnlich aus ei­ner Kunststoffolie hergestellt. Sie haben eine dichte Ober­fläche, eine geringe Masse und sind beständig gegen die mei­sten Säuren, Oele, Lösungsmittel sowie gegen relativ hohe Temperaturen und werden darum vorzugsweise für die Absorp­tion von Luftschall in lärmigen Werkhallen und zum Ausklei­den der Gehäuse von Lärmquellen, insbesondere Verbrennungs­motoren, verwendet.Components of the type described are usually made from a plastic film. They have a dense surface, a low mass and are resistant to most acids, oils, solvents as well as to relatively high temperatures and are therefore preferably used for the absorption of airborne noise in noisy workshops and for lining the housing of noise sources, especially internal combustion engines.

Die bekanntesten Ausführungsformen solcher Bauelemente las­sen sich einer von zwei unterschiedlichen Gruppen zuordnen. Bei der einen Gruppe (DE-OS 27 58 041) sind die rückseiti­gen, d.h. dem einfallenden Schallfeld abgewandten Oeffnungen der Ausstülpungen verschlossen, damit die Masse der schwin­genden Deckfläche mit der eingeschlossenen Luft ein physika­lisches Masse-Feder-System mit einer deutlichen Resonanzfre­quenz bildet. Bei der anderen Gruppe (CH 626 936) sind die rückseitigen Oeffnungen der Ausstülpungen unverschlossen.The best known embodiments of such components can be assigned to one of two different groups. In one group (DE-OS 27 58 041) the rear openings, ie the openings of the protuberances facing away from the incident sound field, are closed so that the mass of the vibrating cover surface with the enclosed air forms a physical mass-spring system with a clear resonance frequency. In the other group (CH 626 936) the rear openings of the protuberances are not closed.

Bei der Verwendung werden die Bauelemente beider Gruppen vorzugsweise vor einer schallreflektierenden Wand und von dieser beabstandet angeordnet.When in use, the components of both groups are preferably arranged in front of and at a distance from a sound-reflecting wall.

In den Publikationen, die Ausführungsformen dieser beiden Gruppen von Bauelementen betreffen, wird erwähnt, dass die Resonanzfrequenz der Deck- bzw. Resonanzfläche von der Form, der Grösse und der Masse dieser Fläche, von der Höhe der Ausstülpung sowie vom mechanischen Verlustfaktor und dem Elastizitätsmodul des verwendeten Materials abhängig ist. Dazu hat die praktische Erfahrung bestätigt, dass auch rela­tiv geringe Unterschiede der Abmessungen der Ausstülpungen den Verlauf sowohl der Schallabsorption in Abhängigkeit von der Frequenz des auftreffenden Schalls als auch die Stärke der Schallabsorption stark beeinträchtigen. Trotz dieser Er­kenntnisse ist bisher noch kein Verfahren zum Herstellen solcher Bauelemente bekannt, das es ermöglicht, die Form und Abmessungen der Resonanzflächen unter Berücksichtigung der Materialeigenschaften für eine vorgegebene Verwendung zu op­timieren.In the publications relating to embodiments of these two groups of components, it is mentioned that the resonance frequency of the cover or resonance surface depends on the shape, size and mass of this surface, on the height of the protuberance and on the mechanical loss factor and the modulus of elasticity of the used material is dependent. Practical experience has confirmed that even relatively small differences in the dimensions of the protuberances severely impair the course of both the sound absorption depending on the frequency of the incident sound and the strength of the sound absorption. Despite these findings, no method for producing such components is known to date which enables the shape and dimensions of the resonance surfaces to be optimized for a given use, taking into account the material properties.

Bei der Verwendung schallabsorbierender Bauelemente in un­mittelbarer Nähe einer Schallquelle ist die maximal zulässi­ge Höhe der Ausstülpungen oft durch die Form und Abmessungen der Schallquelle bzw. deren Verkleidung vorgegeben und ist meistens kleiner als bei den oben erwähnten bekannten Aus­führungsformen. Der vorliegenden Erfindung lag darum die Aufgabe zugrunde, ein Verfahren zu schaffen, das die Her­stellung von Luftschall absorbierenden Bauelementen ermög­licht, die in Abhängigkeit von der zulässigen Höhe der Aus­stülpungen optimale Absorprionseigenschaften aufweisen.When using sound-absorbing components in the immediate vicinity of a sound source, the maximum permissible height of the protuberances is often predetermined by the shape and dimensions of the sound source or its cladding and is usually smaller than in the known embodiments mentioned above. The present invention was therefore based on the object of creating a method which enables the production of airborne sound-absorbing components which have optimum absorption properties as a function of the permissible height of the protuberances.

Ausgehend von der Ueberlegung, dass die Schallabsorption ei­nes schwingungsfähigen Systems, bestehend aus biegeschwin­genden Flächen und einer dahinterliegenden Luftschicht am grössten ist, wenn die Resonanzfrequenz f₀ reell und unge­fähr gleich der spezifischen Impedanz Z₀ der Luft ist, wur­den theoretische und experimentelle Untersuchungen durchge­führt, um ein Verfahren zum Herstellen eines schallabsorbie­renden Bauelements zu schaffen, bei dem die Schallabsorption für einen den praktischen Anforderungen entsprechenden Be­reich der Höhe der Ausstülpungen optimiert ist und im Be­reich der Resonanzfrequenz nur eine geringe Frequenzabhän­gigkeit aufweist.Based on the consideration that the sound absorption of a vibratory system, consisting of bending surfaces and an air layer behind it, is greatest when the resonance frequency is real and approximately equal to the specific impedance Z₀ of the air, theoretical and experimental investigations were carried out, one method to create a sound-absorbing component in which the sound absorption is optimized for a range of the protuberances corresponding to practical requirements and has only a low frequency dependence in the range of the resonance frequency.

Diese Aufgabe wurde mit einem Verfahren der eingangs genann­ten Art gelöst, bei dem für eine optimale Schallabsorption durch Resonanzschwingungen die Dicke d der Resonanzflächen entsprechend der Formel

Figure imgb0001
und die Flächengrösse A jeder Resonanzfläche entsprechend der Formel
Figure imgb0002
 ausgebildet werden, in welcher Formel h die Höhe der Aus­stülpungen bzw. der Abstand von einer schallreflektierenden Wand und f₀ die Resonanzfrequenz ist und K₁, K₂ und K₃ vom Material des Bauelements und von der Schwingungsform der Re­sonanzfläche abhängige Konstante sind.This object was achieved with a method of the type mentioned in the introduction, in which the thickness d of the resonance surfaces corresponds to the formula for optimum sound absorption by resonance vibrations
Figure imgb0001
 and the area size A of each resonance area according to the formula
Figure imgb0002
 are formed, in which formula h the height of the protuberances or the distance from a sound-reflecting wall and f₀ is the resonance frequency and K₁, K₂ and K₃ are dependent on the material of the component and the shape of the resonance surface depending.

Als Schwingungsform s = 1 werden nachfolgend solche Schwin­gungen bezeichnet, die im Längsschnitt durch eine an ihren seitlichen Kanten befestigte Resonanzfläche nur einen Schwingungsbauch aufweisen, als Schwingungsform s = 2 werden Schwingungen bezeichnet, die im gleichen Längsschnitt drei Schwingungsbäuche (und dazwischen zwei Schwingungsknoten) zeigen.In the following, vibrations form s = 1 are those vibrations that have only one antinode in longitudinal section due to a resonance surface attached to their lateral edges, oscillation form s = 2 are oscillations that show three antinodes (and in between two oscillation nodes) in the same longitudinal section.

Zahlenwerte für die Konstante K₁, K₂ und K₃ für zwei ge­bräuchliche unterschiedliche Materialien und die beiden Schwingungsformen s = 1 und s = 2 sind in der folgenden Ta­belle angegeben:

Figure imgb0003
Das erfindungsgemässe Verfahren ermöglicht, die für eine wirksame Schallabsorption durch Resonanzschwingungen wich­tigen Werte, nämlich die Dicke und die Grösse der Resonanz­fläche in Abhängigkeit von der Höhe der Ausstülpung auszu­bilden und damit bisher nicht oder bestenfalls zufällig er­reichte Werte der Schallabsorption systematisch und reprodu­zierbar zu verwirklichen.Numerical values for the constant K₁, K₂ and K₃ for two commonly used different materials and the two waveforms s = 1 and s = 2 are given in the following table:
Figure imgb0003
 The method according to the invention enables the values important for effective sound absorption by resonance vibrations, namely the thickness and the size of the resonance surface, to be designed as a function of the height of the protuberance, and thus systematically and reproducibly to achieve values of sound absorption that have hitherto not been achieved or, at best, at random.

Nachfolgend wird das erfindungsgemässe Verfahren anhand ei­niger Ausführungsformen von Luftschall absorbierenden Bau­elementen und mit Hilfe der Figuren erläutert. Es zeigen:

  • Fig. 1a die perspektivische Draufsicht auf einen Teil eines typischen zur Absorption von Luftschall geeigneten Bauelements mit pyramidenstumpfförmigen Ausstülpun­gen,
  • Fig. 1b den Schnitt durch das in Fig. 1a gezeigte Bauelement längs der Linie X-X,
  • Fig. 2a die grafische Darstellung der erfindungsgemäss be­stimmten Werte für die optimale Dicke d und die op­timale Grösse A einer Resonanzfläche aus kompakter PVC-Folie in Abhängigkeit von der Höhe h der Aus­stülpung und für eine Resonanzfrequenz von f₀ = 1000 Hz,
  • Fig. 2b die zur Fig. 2a analoge Darstellung für eine Reso­nanzfläche aus geschäumter Polypropylen-Folie und für eine Resonanzfrequenz von f₀ = 1600 Hz,
  • Fig. 3 den Verlauf des Schallpegels des von einem Verbren­nungsmotor erzeugten Lärms in Abhängigkeit von der Frequenz, und
  • Fig. 4 den Schallabsorptionskoeffizienten für ein Bauele­ment der bisher bekannten Art und für zwei erfin­dungsgemässe Bauelemente, ebenfalls in Abhängigkeit von der Frequenz.
The method according to the invention is explained below on the basis of some embodiments of airborne sound-absorbing components and with the aid of the figures. Show it:
  • 1a the perspective top view of a part of a typical component suitable for the absorption of airborne sound with truncated pyramidal protuberances,
  • 1b shows the section through the component shown in Fig. 1a along the line XX,
  • 2a shows the graphic representation of the values determined according to the invention for the optimal thickness d and the optimal size A of a resonance surface made of compact PVC film as a function of the height h of the protuberance and for a resonance frequency of f₀ = 1000 Hz,
  • 2b the representation analogous to FIG. 2a for a resonance surface made of foamed polypropylene film and for a resonance frequency of f₀ = 1600 Hz,
  • 3 shows the course of the sound level of the noise generated by an internal combustion engine as a function of the frequency, and
  • Fig. 4 shows the sound absorption coefficient for a component of the previously known type and for two components according to the invention, also as a function of the frequency.

Die Figuren 1a und 1b sind der deutlicheren Darstellung we­gen nicht massstäblich gezeichnet.Figures 1a and 1b are not drawn to scale for clarity.

Das in den Fig. 1a und 1b gezeigte Luftschall absorbierende Bauelement enthält eine Grundfläche 10, deren umlaufender Rand mit einem stabilisierenden Rahmen 11 versehen ist. Die Grundfläche weist eine Mehrzahl gleichartiger pyramiden­stumpfförmiger Ausstülpungen auf, von denen einfacherweise nur die Ausstülpung 12 mit einem Bezugszeichen identifiziert ist. Jede Ausstülpung enthält vier seitliche Flächen 13, 14, 15 und 16 und eine Deckfläche 17. Für die vorliegende Erfin­dung wichtige Grössen der Ausstülpungen sind deren Höhe h sowie die Dicke d und die Grösse A der als bestimmende Reso­nanzfläche wirksamen Deckfläche. Schallabsorptionsmessungen haben gezeigt, dass der horizontale Abstand zwischen benach­barten Ausstülpungen und der Neigungswinkel der Seitenwände zur Grundfläche den Verlauf des Schallabsorptionskoeffizien­ten in Abhängigkeit von der Frequenz wenig beeinflussen. Für eine möglichst grosse Gesamtschallabsorption sind darum die Ausstülpungen vorzugsweise so nahe benachbart und die Sei­tenwände so wenig geneigt auszubilden, wie es das Herstell­verfahren und praktische Bedürfnisse ermöglichen.The airborne sound absorbing component shown in FIGS. 1a and 1b contains a base area 10, the peripheral edge of which is provided with a stabilizing frame 11. The base area has a plurality of similar truncated pyramidal protuberances, of which simply the protuberance 12 is simply identified by a reference symbol. Each protuberance contains four lateral surfaces 13, 14, 15 and 16 and a cover surface 17. The sizes of the protuberances which are important for the present invention are their height h and the thickness d and the size A of the cover surface which acts as the determining resonance surface. Sound absorption measurements have shown that the horizontal distance between adjacent protuberances and the angle of inclination of the side walls to the base surface have little influence on the course of the sound absorption coefficient depending on the frequency. For the greatest possible total sound absorption, the protuberances are therefore preferably as close to one another and the side walls are designed to be as slightly inclined as the manufacturing process and practical requirements allow.

Zur Herstellung des Bauelements kann einfacherweise eine Kunststoffolie tiefgezogen werden. Es ist aber auch möglich, das Bauelement im Kunststoffspritzguss herzustellen oder aus einzelnen miteinander verbundenen Teilflächen gebildete Aus­stülpungen auf eine Trägerfolie zu kleben oder zu schweis­sen. Geeignete Kunststoffe sind beispielsweise Polyvinyl­chlorid, Polyäthylen, Polypropylen, Acrylnitril-Butadien-­Styrol-Polymerisat oder Polykarbonat, die sowohl in kompak­ter wie in geschäumter Form verwendet werden können. Ausge­ hend davon, dass die Wahl eines für einen gegebenen Verwen­dungszweck bestgeeigneten Kunststoff ebenso wie dessen Ver­arbeitung im Bereich fachmännischen Könnens liegen, wird auf eine ausführliche Beschreibung der brauchbaren Materialien und deren Verarbeitung ausdrücklich verzichtet.A plastic film can simply be thermoformed to produce the component. However, it is also possible to manufacture the component in plastic injection molding or to glue or weld protuberances formed from individual sub-areas connected to one another on a carrier film. Suitable plastics are, for example, polyvinyl chloride, polyethylene, polypropylene, acrylonitrile-butadiene-styrene polymer or polycarbonate, which can be used both in compact and in foamed form. Except Due to the fact that the choice of a plastic that is best suited for a given purpose as well as its processing are within the range of expert knowledge, a detailed description of the usable materials and their processing is expressly omitted.

In den Fig. 2a und 2b sind die Membrandicke d und die Mem­branfläche A in Abhängigkeit von der Höhe h der Ausstülpung für einen kompakten bzw. einen geschäumten Kunststoff darge­stellt.2a and 2b show the membrane thickness d and the membrane surface A as a function of the height h of the protuberance for a compact or a foamed plastic.

In Fig. 2a entspricht die Kurve 21 der erfindungsgemäss op­timalen Dicke d der als Resonanzfläche wirksamen Deckfläche der Ausstülpung in Abhängigkeit von der Höhe h der Ausstül­pung für die Schwingungsform s = 1 und einen kompakten PVC-­Kunststoff. Die Kurve 22 zeigt ebenfalls die optimale Dicke d der gleichen Fläche in Abhängigkeit von der Höhe h, aber für die Schwingungsform s = 2. Beide Kurven gelten für eine optimale Resonanzfrequenz bzw. optimale Schallabsorp­tion im Frequenzbereich f₀ ≃ 1000 Hz.In FIG. 2a, curve 21 corresponds to the optimal thickness d according to the invention of the cover surface of the protuberance which acts as a resonance surface as a function of the height h of the protuberance for the vibration form s = 1 and a compact PVC plastic. Curve 22 also shows the optimal thickness d of the same surface as a function of height h, but for waveform s = 2. Both curves apply to an optimal resonance frequency or optimal sound absorption in the frequency range f₀ ≃ 1000 Hz.

Die Kurve 23 entspricht der erfindungsgemäss optimalen Grös­se A der Resonanzfläche in Abhängigkeit von der Höhe h der Ausstülpung für die Schwingungsform s = 1 und einen kompak­ten PVC-Kunststoff. Die Kurve 24 zeigt ebenfalls die optima­le Fläche A in Abhängigkeit von der Höhe h, aber für die Schwingungsform s = 2. Auch diese beiden Kurven gelten für eine Resonanzfrequenz im Bereich f₀ ≃ 1000 Hz.Curve 23 corresponds to the optimal size A of the resonance surface according to the invention as a function of the height h of the protuberance for the vibration form s = 1 and a compact PVC plastic. Curve 24 also shows the optimal area A as a function of the height h, but for the waveform s = 2. These two curves also apply to a resonance frequency in the range f₀ ≃ 1000 Hz.

In Fig. 2b ist die erfindungsgemässe optimale Dicke d der Resonanzfläche in Abhängigkeit von der Höhe h der Ausstül­pung und für die Schwingungsform s = 1 durch die Kurve 25 sowie für die Schwingungsform s = 2 durch die Kurve 26 für ein Bauelement aus geschäumtem Polypropylen-Kunststoff dar­gestellt. Beide Kurven gelten für eine Resonanzfrequenz bzw. eine optimale Schallabsorption im Frequenzbereich f₀ ≃ 1600 Hz.2b, the optimal thickness d of the resonance surface according to the invention is a function of the height h of the protuberance and for the waveform s = 1 by the curve 25 and for the waveform s = 2 represented by curve 26 for a component made of foamed polypropylene plastic. Both curves apply for a resonance frequency or an optimal sound absorption in the frequency range f≃ ≃ 1600 Hz.

Weiter zeigt die Kurve 27 die erfindungsgemäss optimale Grösse A der Resonanzfläche in Abhängigkeit von der Höhe h der Ausstülpung für die Schwingungsform s = 1 und die Kurve 28 die gleiche Grösse für die Schwingungsform s = 2 für ei­nen geschäumten Polypropylen-Kunststoff. Beide Kurven gelten für eine Resonanzfrequenz bzw. eine optimale Schallabsorp­tion im Frequenzbereich f₀ ≃ 1600 Hz.Furthermore, curve 27 shows the optimum size A of the resonance surface according to the invention as a function of the height h of the protuberance for the vibration shape s = 1 and curve 28 shows the same size for the vibration shape s = 2 for a foamed polypropylene plastic. Both curves apply to a resonance frequency or optimal sound absorption in the frequency range f≃ ₀ 1600 Hz.

Aus diesen Kurven ist zu ersehen, dass die optimale Dicke d der Resonanzfläche kleiner wird, wenn die Höhe h der Aus­stülpung grösser wird. Die Kurven bestätigen, dass die Dicke d der Resonanzfläche in dem für die praktische Verwen­dung des Bauelements wichtigen Bereich der Höhe h der Aus­stülpung, d.h. zwischen 10 und 35 mm am stärksten von dieser Höhe abhängig ist. Die Kurven bestätigen weiter, dass für Schwingungsformen s = 2 Ausstülpungen mit Höhen im ge­zeigten Bereich von 10 bis 50 mm die optimale Dicke d auf Werte sinkt, bei denen die geforderte mechanische Stabilität des fertigen Bauelements nicht mehr gewährleistet ist.It can be seen from these curves that the optimal thickness d of the resonance surface becomes smaller as the height h of the protuberance increases. The curves confirm that the thickness d of the resonance surface is within the range of the height h of the protuberance which is important for the practical use of the component, i.e. between 10 and 35 mm is most dependent on this height. The curves further confirm that for waveforms s = 2 protuberances with heights in the range from 10 to 50 mm shown, the optimum thickness d drops to values at which the required mechanical stability of the finished component is no longer guaranteed.

Aus der Darstellung ist ersichtlich, dass sich die optimale Grösse A der Resonanzfläche ungefähr proportional zur Reso­nanzflächendicke d verhält. Die Kurven zeigen ferner, dass die optimale Fläche A für die Schwingungsform s = 2 kleiner ist als für die Schwingungsform s = 1 und dass die dem er­findungsgemässen Verfahren entsprechenden Werte der Dicke d und der Grösse A der Resonanzfläche wesentlich unter den Werten liegen, die bisher gebräuchlich waren und in den ein­gangs genannten Publikationen aufgeführt sind.It can be seen from the illustration that the optimal size A of the resonance surface is approximately proportional to the resonance surface thickness d. The curves also show that the optimal area A for the waveform s = 2 is smaller than for the waveform s = 1 and that the values of the thickness d corresponding to the method according to the invention and the size A of the resonance area are significantly below the values that were previously used and are listed in the publications mentioned at the beginning.

Schliesslich zeigt der Vergleich der Kurven in den Fig. 2a und 2b, dass die Abhängigkeit der für eine optimale Schall­absorption bestimmten Dicke und Grösse der Resonanzfläche von der Höhe der Ausstülpung für eine Resonanzfläche aus ge­schäumtem Kunststoff sehr viel stärker ist als für eine Re­sonanzfläche aus kompaktem Kunststoff.Finally, the comparison of the curves in FIGS. 2a and 2b shows that the dependence of the thickness and size of the resonance surface, which is intended for optimal sound absorption, on the height of the protuberance is much stronger for a resonance surface made of foamed plastic than for a resonance surface made of compact plastic .

Die Fig. 3 zeigt den typischen Verlauf des Schallpegels in Abhängigkeit von der Frequenz für einen Verbrennungsmotor (Viertakt-Ottomotor) mit vier Zylindern und im Leerlauf bei etwa 800 Umdrehungen/Minute. Dabei versteht sich, dass der genaue Verlauf dieser Kurve nicht nur von der genannten Mo­torenart, der Umdrehungszahl und der Belastung, sondern auch von spezifischen Konstruktionsmerkmalen, der Betriebstempe­ratur und weiteren Parametern bestimmt wird. Messungen an unterschiedlichen Motoren bei unterschiedlichen Betriebsbe­dingungen haben jedoch gezeigt, dass der Verlauf der Kurve 30 einem Mittelwert entspricht. Die Kurve 30 zeigt, dass der Schallpegel bei Frequenzen bis 1000 Hz klein ist, mit zuneh­menden Frequenzen ansteigt, bei 1600 Hz den Maximalwert er­reicht, bis etwa 2500 Hz langsam und bei noch höheren Fre­quenzen rasch absinkt.3 shows the typical course of the sound level as a function of the frequency for an internal combustion engine (four-stroke gasoline engine) with four cylinders and at idle at about 800 revolutions / minute. It goes without saying that the exact course of this curve is determined not only by the type of engine mentioned, the number of revolutions and the load, but also by specific design features, the operating temperature and other parameters. However, measurements on different motors under different operating conditions have shown that the curve 30 corresponds to an average value. Curve 30 shows that the sound level is low at frequencies up to 1000 Hz, increases with increasing frequencies, reaches the maximum value at 1600 Hz, slowly decreases until around 2500 Hz and rapidly decreases at even higher frequencies.

Die Fig. 4 zeigt die Stärke der Schallabsorption in Abhän­gigkeit von der Frequenz des auftreffenden Schalls für drei verschiedene Ausführungsformen von Luftschall absorbierenden Bauelementen. Alle drei Bauelemente weisen rückseitig offe­ne, pyramidenstumpfförmige Ausstülpungen auf, wie es in den Fig. 1a und 1b gezeigt ist. Bei allen drei Ausführungsformen wurden die Kunststoff-Folien derart tiefgezogen, dass die Seitenflächen um ca. 20° gegenüber der Senkrechten geneigt sind und die Ausstülpungen in der Ebene der Grundfläche ei­nen Abstand von 5 mm haben.4 shows the strength of the sound absorption as a function of the frequency of the incident sound for three different embodiments of airborne sound absorbing components. All three components have truncated pyramid-shaped protuberances on the back, as in the 1a and 1b is shown. In all three embodiments, the plastic foils were deep-drawn in such a way that the side surfaces are inclined by approximately 20 ° with respect to the vertical and the protuberances are 5 mm apart in the plane of the base surface.

Die Höhe der Ausstülpungen und die Grösse der Resonanzflä­chen ist für alle drei Ausführungsformen gleich und beträgt 30 mm bzw. 35 cm². Die Resonanzflächen sind bei diesen Aus­führungsformen rechteckig und weisen ein Seitenverhältnis von etwa 0,8 : 1 auf.The height of the protuberances and the size of the resonance surfaces are the same for all three embodiments and are 30 mm and 35 cm². In these embodiments, the resonance surfaces are rectangular and have an aspect ratio of approximately 0.8: 1.

Die Kurve 41 zeigt die Schallabsorption eines Bauelements aus geschäumtem Polyäthylen, bei dem die Dicke der Resonanz­fläche 1,5 mm beträgt. Diese Kurve steigt von Werten gerin­ger Schallabsorption bei niedrigen Frequenzen gleichmässig an bis zu einer maximalen Schallabsorption entsprechend αs ∼ 0,8 bei 1000 Hz, fällt dann bis zu Frequenzen von etwa 1250 Hz nur wenig und danach bis etwa 1500 hz steil ab auf αs ∼ 0,3.Curve 41 shows the sound absorption of a component made of foamed polyethylene, in which the thickness of the resonance surface is 1.5 mm. This curve rises evenly from values of low sound absorption at low frequencies to a maximum sound absorption corresponding to α s ∼ 0.8 at 1000 Hz, then drops only slightly up to frequencies of around 1250 Hz and then drops steeply to α s up to around 1500 hz ∼ 0.3.

Die Kurve 42 zeigt die Schallabsorption eines Bauelements aus kompakten PVC, bei dem die Dicke der Resonanzfläche 0,15 mm beträgt. Die Kurve beginnt bei höheren Frequenzen als die Kurve 41, steigt steil an und erreicht für eine Frequenz von 1000 Hz einen relativ schmalen Maximalwert von α s ∼ 0,9 und fällt danach wieder steil ab bis α s ∼ 0,45 bei 1500 Hz.Curve 42 shows the sound absorption of a component made of compact PVC, in which the thickness of the resonance surface is 0.15 mm. The curve begins at higher frequencies than curve 41, rises steeply and reaches a relatively narrow maximum value of α s ∼ 0.9 for a frequency of 1000 Hz and then drops steeply again until α s ∼ 0.45 at 1500 Hz.

Die Kurve 43 zeigt die Schallabsorption eines Bauelements aus geschäumtem Polypropylen, bei dem die Dicke der Reso­nanzflächen 3 mm beträgt. Diese Kurve steigt bis zu Frequen­ zen von etwa 1250 Hz ähnlich an wie die Kurve 41, steigt dann aber weiter bis zu einem Maximalwert von mehr als 0,95 im Frequenzbereich um 1500 Hz und fällt danach flacher als die Kurven 41 und 42 ab und erreicht einen Wert von α s ∼ 0,5 bei einer Frequenz von 4000 Hz.Curve 43 shows the sound absorption of a component made of foamed polypropylene, in which the thickness of the resonance surfaces is 3 mm. This curve rises to frequencies zen of approximately 1250 Hz similar to curve 41, but then continues to rise to a maximum value of more than 0.95 in the frequency range around 1500 Hz and then falls more flatly than curves 41 and 42 and reaches a value of α s ∼ 0.5 at a frequency of 4000 Hz.

Die gezeigten Kurven machen deutlich, dass die Schallabsorp­tion von geschäumtem Kunststoff höhere Werte erreicht und in einem breiteren Frequenzbereich wirksam ist als diejenige von kompaktem Kunststoff und dass ein Bauelement mit erfin­dungsgemäss dimensionierten Ausstülpungen (Kurve 43) eine Schallabsorptionskurve aufweist, die sehr gut mit dem Schallpegel eines Verbrennungsmotors (Fig. 3) übereinstimmt.The curves shown make it clear that the sound absorption of foamed plastic achieves higher values and is effective in a wider frequency range than that of compact plastic and that a component with protuberances dimensioned according to the invention (curve 43) has a sound absorption curve which is very good at the sound level of a Internal combustion engine (Fig. 3) matches.

Es versteht sich, dass das erfindungsgemässe Verfahren und ein nach diesem Verfahren herstelltes Bauelement an speziel­le Arbeitsbedingungen oder Verwendungen angepasst werden kann. Es wurde bereits erwähnt, dass anstelle der für die beschriebenen Ausführungsbeispiele verwendeten Folien auch andere Kunststoff-Folien mit ähnlichen Eigenschaften verwen­det werden können. Es ist auch möglich, das Bauelement an­ders als die beschriebene einfache, mit Ausstülpungen verse­hene Kunststoff-Folie auszubilden. Für bestimmte Verwendun­gen kann es vorteilhaft sein, die Rückseite des Bauelements mit einem porösen, schallschluckenden Material zu belegen oder in bzw. auf die rückseitigen Oeffnungen der Ausstülpun­gen einen "Deckel" aus solchem Material ein- oder aufzuset­zen. Weiter ist es möglich, mit zwei Bauelementen der be­schriebenen Art ein kombiniertes Bauelement herzustellen. Von den dafür vertwendeten einfachen Bauelementen ist das ei­ne mit Ausstülpungen zu versehen, die etwas höher und deren Grundfläche etwas grösser ist als bei dem anderen. Diese Ausbildung der Ausstölpungen ermöglicht, die Bauelemente derart aufeinanderzulegen, dass nur die zwischen den Aus­stülpungen angeordneten Stege der Grundflächen aufeinander­liegen. Dann bilden die übereinanderstehenden Ausstülpungen einen geschlossenen und einen rückwärtig offenen Resonanz­raum, womit die Schallabsorption und deren Frequenzbereich nochmals verbessert bzw. erweitert werden können. Schliess­lich ist es auch möglich, aus mehr als zwei Bauelementen ein kombiniertes Bauelement herzustellen.It goes without saying that the method according to the invention and a component produced using this method can be adapted to special working conditions or uses. It has already been mentioned that instead of the films used for the exemplary embodiments described, other plastic films with similar properties can also be used. It is also possible to design the component differently than the simple plastic film provided with protuberances. For certain uses, it may be advantageous to cover the back of the component with a porous, sound-absorbing material or to insert or put a "cover" of such material in or on the rear openings of the protuberances. It is also possible to produce a combined component with two components of the type described. Of the simple components used for this, one is to be provided with protuberances that are somewhat higher and whose base area is somewhat larger than the other. These Formation of the protuberances enables the components to be placed on one another in such a way that only the webs of the base surfaces arranged between the protuberances lie one on top of the other. Then the overlapping protuberances form a closed and a rearwardly open resonance space, with which the sound absorption and its frequency range can be further improved or expanded. Finally, it is also possible to produce a combined component from more than two components.

Claims (12)

1. Verfahren zum Herstellen eines Luftschall absorbierenden Bauelements, das eine Mehrzahl becherförmige Ausstülpun­gen aufweist, deren als Resonanzflächen wirksame Deck­flächen von auftreffender Schallenergie zu Schwingungen angeregt werden, wobei die Schallenergie mindestens teil­weise absorbiert und in Wärme umgewandelt wird,
dadurch gekennzeichnet, dass für eine optimale Schallab­sorption durch Resonanzschwingungen die Dicke d der Resonanzflächen entsprechend der Formel
Figure imgb0004
 und die Flächengrösse A jeder Resonanzfläche entsprechend der Formel
Figure imgb0005
 ausgebildet werden,
in welchen Formeln h die Höhe der Ausstülpung und f₀ die Resonanzfrequenz ist und K₁, K₂ und K₃ vom Material des Bauelements und von der Schwingungsform der Resonanzflä­che abhängige Konstante sind.1. A method for producing an airborne sound-absorbing component which has a plurality of cup-shaped protuberances whose top surfaces which act as resonance surfaces are excited to vibrate by impinging sound energy, the sound energy being at least partially absorbed and converted into heat,
characterized in that for an optimal sound absorption by resonance vibrations the thickness d of the resonance surfaces according to the formula
Figure imgb0004
 and the area size A of each resonance area according to the formula
Figure imgb0005
 be formed,
in which formulas h is the height of the protuberance and f₀ is the resonance frequency and K₁, K₂ and K₃ are dependent on the material of the component and on the waveform of the resonance surface. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass für ein Bauelement aus kompaktem Kunststoff und Resonanz­schwingungen im Bereich von 1000 Hz sowie die Schwin­gungsform s = 1 der Wert für die Konstante K₁ = 1,1 ms⁻¹, für die Konstante K₂ = 1,6 m²s⁻² und für die Konstante K₃ = 4,7.10³ ms⁻¹ ist.2. The method according to claim 1, characterized in that for a component made of compact plastic and resonant vibrations in the range of 1000 Hz and the waveform s = 1, the value for the constant K₁ = 1.1 ms⁻¹, for the constant K₂ = 1 , 6 m²s⁻² and for the constant K₃ = 4.7.10³ ms⁻¹. 3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass für ein Bauelement aus kompaktem Kunststoff und Resonanz­schwingungen im Bereich von 1000 Hz sowie der Schwin­gungsform s = 2 (Oberschwingung) der Wert für die Kon­stante K₁ = 0,12 ms⁻¹, für die Konstante K₂ = 0,17 m²s⁻² und für die Konstante K₃ = 2,1.10⁴ ms⁻¹ ist.3. The method according to claim 1, characterized in that for a component made of compact plastic and resonant vibrations in the range of 1000 Hz and the waveform s = 2 (harmonic), the value for the constant K₁ = 0.12 ms⁻¹, for the constant K₂ = 0.17 m²s⁻² and for the constant K₃ = 2.1.10⁴ ms⁻¹. 4. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass für ein Bauelement aus geschäumtem Kunststoff und der Schwingungsform s = 1 der Wert für die Konstante K₁ = 3,2 ms⁻¹, für die Konstante K₂ = 70,6 m²s⁻² und für die Konstante K₃ = 1,5.10³ ms⁻¹ ist.4. The method according to claim 1, characterized in that for a component made of foamed plastic and the waveform s = 1, the value for the constant K₁ = 3.2 ms⁻¹, for the constant K₂ = 70.6 m²s⁻² and for the constant K₃ = 1.5.10³ ms⁻¹. 5. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass für ein Bauelement aus geschäumtem Kunststoff und der Schwingungsform s = 2 der Wert für die Konstante K₁ = 0,34 ms⁻¹, für die Konstante K₂ = 7,5 m²s⁻² und für die Konstante K₃ = 7,5.10³ ms⁻¹ ist.5. The method according to claim 1, characterized in that for a component made of foamed plastic and the waveform s = 2, the value for the constant K₁ = 0.34 ms⁻¹, for the constant K₂ = 7.5 m²s⁻² and for the constant K₃ = 7.5.10³ ms⁻¹. 6. Nach dem Verfahren gemäss Anspruch 1 hergestelltes Luft­schall absorbierendes Bauelement, gekennzeichnet durch mindestens eine kompakte oder geschäumte Kunststoffolie, aus der die becherförmigen Ausstülpungen einstückig aus­geformt sind.6. Airborne sound absorbing component produced by the method according to claim 1, characterized by at least one compact or foamed plastic film from which the cup-shaped protuberances are formed in one piece. 7. Bauelement nach Anspruch 6, dadurch gekennzeichnet, dass zwei oder mehrer Kunststoffolien mit unterschiedlicher Höhe und Grundfläche der Ausstülpungen derart aufeinan­dergelegt werden, dass nur die zwischen benachbarten Ausstülpungen angeordneten Stege der Grundflächen sich berühren.7. The component according to claim 6, characterized in that two or more plastic films with different heights and base area of the protuberances are placed on top of one another in such a way that only the webs of the base areas arranged between adjacent protuberances touch. 8. Bauelement nach Anspruch 6, dadurch gekennzeichnet, dass die Deck- oder Resonanzflächen der Ausstülpungen die Form eines Rechtecks, eines Trapezes, eines Parallelo­gramms, eines Kreises oder eines regulären Vielecks ha­ben.8. The component according to claim 6, characterized in that the cover or resonance surfaces of the protuberances have the shape of a rectangle, a trapezoid, a parallelogram, a circle or a regular polygon. 9. Bauelement nach Anspruch 8, dadurch gekennzeichnet, dass die becherförmigen Ausstülpungen in Richtung der Deck­fläche verjüngt sind.9. The component according to claim 8, characterized in that the cup-shaped protuberances are tapered in the direction of the top surface. 10. Bauelement nach Anspruch 6, dadurch gekennzeichnet, dass die inneren Oeffnungen der becherförmigen Ausstülpungen mit einer Schicht aus porösem Material verschlossen sind.10. The component according to claim 6, characterized in that the inner openings of the cup-shaped protuberances are closed with a layer of porous material. 11. Verwendung des Bauelements gemäss dem Anspruch 6 zur mindestens teilweisen Innenverkleidung der Verschalung einer Maschine, insbesondere eines Verbrennungsmotors.11. Use of the component according to claim 6 for the at least partial inner lining of the casing of a machine, in particular an internal combustion engine. 12. Verwendung des Bauelementes gemäss dem Anspruch 6 zur mindestens teilweisen Innenverkleidung eines Raumes.12. Use of the component according to claim 6 for at least partially interior cladding of a room.
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DE3776450D1 (en) 1992-03-12
MX168844B (en) 1993-06-11
JPH0818389B2 (en) 1996-02-28
BR8702500A (en) 1988-02-23
CA1277922C (en) 1990-12-18
US4755416A (en) 1988-07-05
ES2030092T3 (en) 1992-10-16
EP0255473B1 (en) 1992-01-29
JPS6327242A (en) 1988-02-04
CH671848B (en) 1989-09-29

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