EP0041260A1 - Sound absorbing element utilizing the effect of coincidence - Google Patents

Sound absorbing element utilizing the effect of coincidence Download PDF

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Publication number
EP0041260A1
EP0041260A1 EP81104147A EP81104147A EP0041260A1 EP 0041260 A1 EP0041260 A1 EP 0041260A1 EP 81104147 A EP81104147 A EP 81104147A EP 81104147 A EP81104147 A EP 81104147A EP 0041260 A1 EP0041260 A1 EP 0041260A1
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Prior art keywords
coincidence
sound
gas
wave
element according
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EP81104147A
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German (de)
French (fr)
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EP0041260B1 (en
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Oskar Dr. Rer. Nat. Bschorr
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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

Definitions

  • the invention relates to a wall element for sound absorption with a closed surface and high mechanical, corrosive and thermal strength using the coincidence effect. It is intended to provide sound insulation and sound insulation in ducts, capsules, rooms and in intake and outlet flows.
  • Absorbent materials of various designs are known for this task. In these, the frictional movement of the sound fast and the absorption material converts the sound into heat. In order to achieve high absorption values, it is important to have a soft, open-pore absorber surface and a sufficient absorber depth. In addition, when using absorbent room walls or ceilings, a minimum distance of about a quarter of the sound wavelength from the absorber to the wall is necessary in order to be in the range of effective rapid movements.
  • a disadvantage of the absorption materials described is their low resistance to mechanical stress, moisture and rotting.
  • the object of the invention is a wall element for sound absorption using the coincidence effect.
  • coincidence transducers are provided which have a volume boost. Compared to the prior art, this also results in sound damping and sound insulation even when sound is applied to both sides. Thanks to the volume stroke, the resulting pressure forces are not canceled even when the front and rear sides are acted on identically, but both sides are individually excited to produce coincidence vibrations. This not only results in a double use of space, but also saves a special covering of one wall side to avoid pressure neutralization.
  • this object is achieved in that flexible waveguides as coincidence waveguides with profile shapes with a high moment of inertia J, z.
  • aluminum, beryllium, steel, GRP and CFRP materials can be used. With these conditions, sufficiently high bending shaft speeds can be achieved with a low basis weight and therefore a high acoustic effect.
  • two coincidence waveguides are connected together essentially in parallel, the gap which is formed being sealed gas-tight and with a gas with high speed of sound, for. B. helium, hydrogen is filled.
  • a gas with high speed of sound for. B. helium, hydrogen is filled.
  • flat or strip-shaped membranes are used as coincidence waveguides which are under a biaxial or uniaxial tensile load, so that the membrane wave speed is equal to the speed of sound of the surrounding medium.
  • the tensile load on flat membrane surfaces can be caused by the edge clamping. Another possibility is to hold curved membrane surfaces under tensile load by one-sided vacuum or vacuum pressure.
  • edges of the oinzidenzwellenleiter as K bending waveguides used are not firmly fixed to each other but able to oscillate freely thanks to a spring-soft compound.
  • the entire length of the coincidence waveguide acts.
  • the rear end of the coincidence waveguide, as seen in the sound direction, is damped. This can be achieved in a manner known per se by a reflection-free termination of the coincidence waveguide.
  • the terminating impedance is matched to that of the flexible waveguide.
  • This mechanism is also used, for example, for the edge damping of window panes using putty.
  • the coincidence waveguides are additionally covered with conventional, porous absorption mats.
  • the high frequencies in particular can thus be damped.
  • F ig. 1 shows the basic design of an absorption element 1. It consists of 2 coincidence conductors 2, which have a trapezoidal shape. There is an intermediate space 3 between the two coincidence conductors 2. The intermediate space 3 is sealed gas-tight to the outside and is sealed with a gas with a high speed of sound, e.g. B. hydrogen or helium filled with ambient pressure.
  • a gas with a high speed of sound e.g. B. hydrogen or helium filled with ambient pressure.
  • the coincidence conductors 2 represent flexible waveguides. Given the wall thickness and trapezoidal height, they have an area moment of inertia J in the axial direction. With the modulus of elasticity E, mass occupancy m and the excitation frequency w, the coincidence conductor has a bending wave velocity C s
  • a plurality of absorption elements 1 tuned to different frequencies are to be used to attenuate broadband noise signals.
  • Materials with a high modulus of elasticity E and a low density e.g. As aluminum, fiber materials such as GRP and CFRP, beryllium and steel.
  • Fig. 2 shows an analogous embodiment to Fig. 1.
  • the absorption element 11 consists of 2 coincidence conductors 12 with a wavy profile.
  • In the intermediate space 13 there is again a gas with a high speed of sound (hydrogen, helium) with ambient pressure and the roller-shaped fixings 14.
  • the coincidence conductors 12 again represent flexible waveguides, the bending wave speed of which depends on that of the surrounding medium.
  • B. air is matched.
  • the absorption elements are attached, for example, in a ventilation duct 15 ′.
  • any desired cross-sectional shapes can be selected.
  • the profile shape serves in particular to increase the moment of inertia and thus. the bending shaft speed.
  • a double-corrugated profile shape of the coincidence waveguide 22 is shown.
  • a pulling mechanism 23 is provided at the same time, by means of which the coincidence waveguides 22 can be stretched (shortened) in the transverse direction. This also changes the profile height and thus the bending shaft speed. In this way, these changed operating conditions can be adapted.
  • An automatic, temperature-dependent control results when using bimetal strips.
  • a pressure-dependent control can be implemented analogously by means of barometer springs.
  • absorption elements 31 are shown in FIG. 4 for broadband sound influencing, the coincidence conductors 32 of which have different profile heights and thus the coincidence speed adapted to the different frequencies of the speed of sound.
  • FIG. 5 shows an absorption element 41 in a longitudinal section. It is characterized in that the profile height of the coincidence ladder 42 increases in the longitudinal direction. Such a measure ensures, as in FIG. 4, that in the case of broadband noise, the individual noise frequencies each find suitable sections with a coincidence condition.
  • FIG. 6 is a cross section through an absorption element 51 with a double tubular coincidence waveguide 52. In the gas-tight space 53 there is again gas with a high speed of sound.
  • FIG. 7 shows the cross section of an absorption element 61 with coincidence waveguides 62 consisting of honeycomb plates, which are joined gas-tight to form the intermediate space 63.
  • the cover plates oriented towards the intermediate space 63 expediently have openings 64, so that a relatively large volume is formed in the intermediate space 63.
  • air can also be provided in the intermediate space 63 instead of a gas with a high speed of sound.
  • FIG. 8 shows an absorption element 71 whose coincidence waveguide 72 executes membrane waves. It is spanned by a back shell 74.
  • the space 73 between the coincidence waveguide 72 and the back shell 74 is evacuated or partially evacuated. In the latter case, the residual gas (hydrogen, helium) has a high speed of sound.
  • the vacuum load results in a tensile load in the coincidence waveguide 72.
  • the tensile load and mass assignment result in a frequency-independent membrane speed in a manner known per se. This is designed for coincidence with the surrounding medium.
  • FIG. 9 shows an absorption element 81 integrated into a tube. It consists of a cylindrical coincidence waveguide 82 which is held by a tube jacket 84. The space 83 between the coincidence waveguide 82 and the tubular jacket 84 is fully or partially evacuated. As a result, there is a voltage in the coincidence waveguide 82, which results in a frequency-independent membrane wave velocity. Thanks to the transverse contraction, the primary ring stresses are also converted into longitudinal stresses, so that the membrane wave velocity can be made equal in both directions to the speed of sound of the medium flowing through the tube.
  • FIG. 10 shows the case inverse to FIG. 9.
  • the absorption element 61 consists of a tubular coincidence waveguide 62. This is at an internal pressure P., the compressed gas consisting of low molecular weight substances with high speed of sound.
  • the membrane pressure can be set to coincidence by the internal pressure.
  • FIG. 11 shows a double-acting absorption element 101, which has tensioned membranes on its outer sides as coincidence waveguides 102.
  • a membrane density of m [kg / m 3 ] they receive a tension ⁇ [N / m], so that the membrane speed equal to the speed of sound of the surrounding medium, e.g. B. is air.
  • the tension ⁇ exists in both diaphragm directions so that sound can be absorbed from all angles.
  • a single-axis membrane tension is sufficient in narrow channels with a preferred direction.
  • the tension itself can be maintained by Federm 105 (e.g. buckling springs). These springs 105 are particularly recommended because of their spring constancy, so that the same membrane tension is always maintained regardless of expansions.
  • the springs 105 itself based on a mean latte p 104..
  • the interior 103 is filled with a gas of high speed of sound.

Abstract

1. Absorption element based on the coincidence effect with a closed surface, characterized by 2 parallel coincidence wave guides with a periodic trapecoidal, corrugated or double-corrugated cross sections, where the areal moment of inertia, the young-moduls and the density of the wave guides, for example aluminium steel, carbon-fiber- plastics, glass-fiber-plastics chosen in such a manner, that for a given excitation frequency the bending wave velocity of the coincidence wave guide corresponds to the tracevelocity of the incidencing sound wave and where the enclosed space between the guides is gas proof sealed and filled with a gas of a high speed of sound such as hydrogen or helium and that for positioning of the coincidence wave guides separators are used.

Description

Die Erfindung bezieht sich auf ein Wandelement zur Schallabsorption mit geschlossener Oberfläche und hoher mechanischer, korrosiver und thermischer Festigkeit unter Ausnützung des Koinzidenzeffektes. Es ist beabsichtigt, eine Schalldämpfung und Schalldämmung in Kanälen, Kapseln, Räumen und bei Ansaug-und Auslaßströmungen herbeizuführen.The invention relates to a wall element for sound absorption with a closed surface and high mechanical, corrosive and thermal strength using the coincidence effect. It is intended to provide sound insulation and sound insulation in ducts, capsules, rooms and in intake and outlet flows.

Bekannt für diese Aufgabenstellung sind Absorptionsmaterialien der verschiedensten Ausführungsformen. Bei diesen wird durch die Reibbewegung von Schallschnelle und Absorptionsstoff der Schall in Wärme übergeführt. Um hohe Absorptionswerte zu erreichen, kommt es darauf an, eine möglichst weiche, offenporige Absorberfläche und eine ausreichende Absorbertiefe zur Verfügung zu haben. Außerdem ist beim Einsatz von absorbierenden Raumwänden bzw. Decken ein Mindestabstand von ca. einem Viertel der Schallwellenlänge vom Absorber zur Wand notwendig, um im Bereich wirksamer Schnellebewegungen zu liegen.Absorbent materials of various designs are known for this task. In these, the frictional movement of the sound fast and the absorption material converts the sound into heat. In order to achieve high absorption values, it is important to have a soft, open-pore absorber surface and a sufficient absorber depth. In addition, when using absorbent room walls or ceilings, a minimum distance of about a quarter of the sound wavelength from the absorber to the wall is necessary in order to be in the range of effective rapid movements.

Ein Nachteil der beschriebenen Absorptionsmaterialien ist deren geringe Widerstandsfähigkeit gegen mechanische Beanspruchung, Feuchtigkeit und Verrottung.A disadvantage of the absorption materials described is their low resistance to mechanical stress, moisture and rotting.

Mit der deutschen Patentanmeldung P 25 31 866 ist ein Wandelement bekannt geworden, das ebenfalls den Koinzidenzeffekt zur Schallabsorption ausnützt. Der Nachteil dieser Konstruktion ist jedoch, daß diese Elemente keine Biegeschwinger sind und keinen Volumenhub aufweisen, Das hat zur Folge, daß diese nicht wirken, wenn sie beidseitig von Schall beaufschlagt sind.With the German patent application P 25 31 866 a wall element has become known which also uses the coincidence effect for sound absorption. The disadvantage of this construction, however, is that these elements are not flexural vibrators and have no volume stroke, which means that they do not work if sound is applied to them on both sides.

Aufgabe der Erfindung ist ein Wandelement zur Schallabsorption unter Ausnützung des Koinzidenzeffektes. Im besonderen sind Koinzidenzschwinger vorgesehen, die einen Volumenschub aufweisen. Damit ergibt sich gegenüber dem Stand der Technik auch eine Schalldämpfung und Schalldämmung auch bei beidseitiger Beaufschlagung mit Schall. Dank des Volumenhubes kommt es auch bei identischer Beaufschlagung der Vorder- und Rückseite zu keiner Aufhebung der resultierenden Druckkräfte, sondern beide Seiten werden individuell zu Koinzidenzschwingungen angeregt. Das ergibt nicht nur eine doppelte Flächenausnützung, sondern erspart auch eine spezielle Abdeckung einer Wandseite zur Vermeidung einer Druckneutralisation.The object of the invention is a wall element for sound absorption using the coincidence effect. In particular, coincidence transducers are provided which have a volume boost. Compared to the prior art, this also results in sound damping and sound insulation even when sound is applied to both sides. Thanks to the volume stroke, the resulting pressure forces are not canceled even when the front and rear sides are acted on identically, but both sides are individually excited to produce coincidence vibrations. This not only results in a double use of space, but also saves a special covering of one wall side to avoid pressure neutralization.

Erfindungsgemäß wird diese Aufgabe dadurch gelöst, daß Biegewellenleiter als Koinzidenzwellenleiter mit Profilformen mit hohem Flächenträgheitsmoment J, z. B. trapezförmig, wellenförmig und aus einem Material mit hohem Elastizitätsmodul E und geringer Dichte j , z. B. Aluminium, Beryllium, Stahl, GFK-und CFK-Materialien verwendet werden. Mit diesen Bedingungen lassen sich bei kleinem Flächengewicht und deshalb hoher akustischer Wirkung ausreichend hohe Biegewellengeschwindigkeiten erreichen.According to the invention this object is achieved in that flexible waveguides as coincidence waveguides with profile shapes with a high moment of inertia J, z. B. trapezoidal, wavy and made of a material with a high modulus of elasticity E and low density j, z. As aluminum, beryllium, steel, GRP and CFRP materials can be used. With these conditions, sufficiently high bending shaft speeds can be achieved with a low basis weight and therefore a high acoustic effect.

Nach einem weiteren Merkmal der Erfindung werden jeweils 2 Koinzidenzwellenleiter im wesentlichen parallel zusammengeschlossen, wobei der sich bildende Zwischenraum gasdicht abgeschlossen und mit einem Gas mit hoher Schallgeschwindigkeit, z. B. Helium, Wasserstoff gefüllt ist. Eine solche Maßnahme ergibt im Zwischenraum dank der hohen Schallgeschwindigkeit Druckausgleich, so daß auch bei kleinem Abstand der Koinzidenzwellenleiter die Federeigenschaften des Gaspolsters weniger stören.According to a further feature of the invention, two coincidence waveguides are connected together essentially in parallel, the gap which is formed being sealed gas-tight and with a gas with high speed of sound, for. B. helium, hydrogen is filled. Such a measure results in pressure equalization in the space thanks to the high speed of sound, so that the spring properties of the gas cushion interfere less even with a small distance between the coincidence waveguides.

Nach einem weiteren Merkmal der Erfindung werden als Koinzidenzwellenleiter flächen- oder streifenförmige Membrane verwendet, die unter einer zwei- oder einachsigen Zugbelastung stehen, so daß die Membranwellengeschwindigkeit gleich der Schallgeschwindigkeit des umgebenden Mediums ist. Die Zugbelastung bei planen Membranflächen kann durch die Randeinspannung erfolgen. Eine andere Möglichkeit besteht darin, durch einseitige Vakuum-oder Unterdruckbelastung gewölbte Membranflächen unter Zugbelastung zu halten.According to a further feature of the invention, flat or strip-shaped membranes are used as coincidence waveguides which are under a biaxial or uniaxial tensile load, so that the membrane wave speed is equal to the speed of sound of the surrounding medium. The tensile load on flat membrane surfaces can be caused by the edge clamping. Another possibility is to hold curved membrane surfaces under tensile load by one-sided vacuum or vacuum pressure.

Nach einem weiteren Merkmal der Erfindung sind die Ränder der als Koinzidenzwellenleiter verwendeten Biegewellenleiter nicht fest gegeneinander fixiert, sondern können dank einer federweichen Verbindung frei schwingen. Dadurch wirkt die gesamte Länge des Koinzidenzwellenleiters. Im weiteren ist das in Schallrichtung gesehen hintere Ende des Koinzidenzwellenleiters bedämpft Dies kann in an sich bekannter Weise durch einen reflexionsfreien Abschluß des Koinzidenzwellenleiters erreicht werden. In diesem Fall ist die Abschlußimpedanz auf die des Biegewellenleiters abgestimmt. Dieser Mechanismus wird beispielsweise auch bei der Randdämpfung von Fensterscheiben mittels Kitt angewendet.According to a further feature of the invention the edges of the oinzidenzwellenleiter as K bending waveguides used are not firmly fixed to each other but able to oscillate freely thanks to a spring-soft compound. As a result, the entire length of the coincidence waveguide acts. Furthermore, the rear end of the coincidence waveguide, as seen in the sound direction, is damped. This can be achieved in a manner known per se by a reflection-free termination of the coincidence waveguide. In this case, the terminating impedance is matched to that of the flexible waveguide. This mechanism is also used, for example, for the edge damping of window panes using putty.

Nach einem weiteren Merkmal der Erfindung werden die Koinzidenzwellenleiter zusätzlich mit konventionellen, porösen Absorptionsmatten abgedeckt. Damit können insbesondere die hohen Frequenzen gedämpft werden.According to a further feature of the invention, the coincidence waveguides are additionally covered with conventional, porous absorption mats. The high frequencies in particular can thus be damped.

Die Erfindung ist anhand der folgenden Zeichnungsbeschreibungen näher erläutert. Es zeigen

  • Fig. 1 bis Fig. 7 Absorptionselemente mit Koinzidenzwellenleitern unter Benützung von Biegewellen,
  • Fig. 8 bis Fig. 11 Absorptionselemente mit Koinzidenzwellenleitern unter Benützung von Membranwellen.
The invention is explained in more detail with reference to the following description of the drawings. Show it
  • 1 to 7 absorption elements with coincidence waveguides using bending waves,
  • 8 to 11 absorption elements with coincidence waveguides using membrane waves.

Fig. 1 zeigt die Grundausführung eines Absorptionselementes 1. Es besteht aus 2 Koinzidenzleitern 2, die eine Trapezform aufweisen. Zwischen den beiden Koinzidenzleitern 2 befindet sich ein Zwischenraum 3. Der Zwischenraum 3 ist gasdicht nach außen abgeschlossen und ist mit einem Gas mit hoher Schallgeschwindigkeit, z. B. Wasserstoff oder Helium mit Umgebungsdruck gefüllt. F ig. 1 shows the basic design of an absorption element 1. It consists of 2 coincidence conductors 2, which have a trapezoidal shape. There is an intermediate space 3 between the two coincidence conductors 2. The intermediate space 3 is sealed gas-tight to the outside and is sealed with a gas with a high speed of sound, e.g. B. hydrogen or helium filled with ambient pressure.

Zur gegenseitigen Fixierung dienen Distanzhalter 4 in Rollenform. Die Koinzidenzleiter 2 stellen Biegewellenleiter dar. Gegeben durch Wandstärke und Trapezhöhe weisen diese in Achsenrichtung ein Flächenträgheitsmoment J auf. Mit dem Elastizitätsmodul E, Massenbelegung m und bei der Anregungsfrequenz w hat der Koinzidenzleiter eine Biegewellengeschwindigkeit Cs

Figure imgb0001
Spacers 4 in roll form serve for mutual fixation. The coincidence conductors 2 represent flexible waveguides. Given the wall thickness and trapezoidal height, they have an area moment of inertia J in the axial direction. With the modulus of elasticity E, mass occupancy m and the excitation frequency w, the coincidence conductor has a bending wave velocity C s
Figure imgb0001

Diese wird nun so gewählt, daß sie mit der Spurgeschwindigkeit C einer unter dem Winkel α einfallenden Schallwelle übereinstimmt.

Figure imgb0002
This is now chosen so that it corresponds to the track speed C of a sound wave incident at the angle α.
Figure imgb0002

Zur Dämpfung breitbandiger Lärmsignale sind mehrere auf verschiedene Frequenzen abgestimmte Absorptionselemente 1 zu verwenden. Bei parallelem Schalleinfall ist insbesondere C = C = CB (C = Schallgeschwindigkeit). Als Material für die Koinzidenzleiter 2 eignen sich insbesondere Stoffe mit hohem Elastizitätsmodul E und kleiner Dichte, z. B. Aluminium, Faserstoffe wie GFK und CFK, Beryllium und auch Stahl.A plurality of absorption elements 1 tuned to different frequencies are to be used to attenuate broadband noise signals. In the case of parallel sound, C = C = C B (C = speed of sound). Materials with a high modulus of elasticity E and a low density, e.g. As aluminum, fiber materials such as GRP and CFRP, beryllium and steel.

Fig. 2 stellt eine analoge Ausführung zu Fig. 1 dar. Das Absorptionselement 11 besteht aus 2 Koinzidenzleitern 12 mit wellenförmigem Profil. Im Zwischenraum 13 befindet sich wieder ein Gas mit hoher Schallgeschwindigkeit (Wasserstoff, Helium) mit Umgebungsdruck und die rollenförmigen Fixierungen 14.Fig. 2 shows an analogous embodiment to Fig. 1. The absorption element 11 consists of 2 coincidence conductors 12 with a wavy profile. In the intermediate space 13 there is again a gas with a high speed of sound (hydrogen, helium) with ambient pressure and the roller-shaped fixings 14.

Die Koinzidenzleiter 12 stellen wieder Biegewellenleiter dar, deren Biegewellengeschwindigkeit auf die des umgebenden Mediums z. B. Luft abgestimmt ist. Die Absorptionselemente sind beispielsweise in einem Lüftungskanal 15'angebracht.The coincidence conductors 12 again represent flexible waveguides, the bending wave speed of which depends on that of the surrounding medium. B. air is matched. The absorption elements are attached, for example, in a ventilation duct 15 ′.

Neben den in den vorangegangenen Beschreibungsbeispielen Trapez-oder Wellenform des Koinzidenzleiters können an sich beliebige Querschnittsformen gewählt werden. Die Profilform dient im besonderen zur Erhöhung des Flächenträgheitsmomentes und damit. der Biegewellengeschwindigkeit. In Fig. 3 beispielsweise ist eine doppelt gewellte Profilform der Koinzidenzwellenleiter 22 dargestellt. In diesem Fall ist gleichzeitig ein Zugmechanismus 23 vorgesehen, durch den die Koinzidenzwellenleiter 22 in Querrichtung gestreckt (verkürzt) werden können. Dadurch ändert sich auch die Profilhöhe und damit die Biegewellengeschwindigkeit. Auf diese Weise kann diese veränderten Betriebsbedingungen angepaßt werden. Eine automatische, temperaturabhängige Regelung ergibt sich bei Verwendung von Bimetallstreifen. Durch Barometerfedern läßt sich analog eine druckabhängige Regelung realisieren.In addition to the trapezoidal or waveform of the coincidence conductor in the previous description examples, any desired cross-sectional shapes can be selected. The profile shape serves in particular to increase the moment of inertia and thus. the bending shaft speed. 3, for example, a double-corrugated profile shape of the coincidence waveguide 22 is shown. In this case, a pulling mechanism 23 is provided at the same time, by means of which the coincidence waveguides 22 can be stretched (shortened) in the transverse direction. This also changes the profile height and thus the bending shaft speed. In this way, these changed operating conditions can be adapted. An automatic, temperature-dependent control results when using bimetal strips. A pressure-dependent control can be implemented analogously by means of barometer springs.

Da die Biegewellengeschwindigkeit frequenzabhängig ist, sind für eine breitbandige Schallbeeinflussung in Fig. 4 Absorptionselemente 31 dargestellt, deren Koinzidenzleiter 32 unterschiedliche Profilhöhe und damit für die unterschiedlichen Frequenzen der Schallgeschwindigkeit angepaßte Koinzidenzgeschwindigkeit aufweisen.Since the bending wave speed is frequency-dependent, absorption elements 31 are shown in FIG. 4 for broadband sound influencing, the coincidence conductors 32 of which have different profile heights and thus the coincidence speed adapted to the different frequencies of the speed of sound.

In Fig. 5 ist ein Absorptionselement 41 im Längsschnitt dargestellt. Es ist dadurch gekennzeichnet, daß die Profilhöhe der Koinzidenzleiter 42 in Längsrichtung anwächst. Eine solche Maßnahme gewährleistet wie in Fig. 4, daß bei breitbandigem Lärm die einzelnen Lärmfrequenzen jeweils passende Abschnitte mit Koinzidenzbedingung finden.5 shows an absorption element 41 in a longitudinal section. It is characterized in that the profile height of the coincidence ladder 42 increases in the longitudinal direction. Such a measure ensures, as in FIG. 4, that in the case of broadband noise, the individual noise frequencies each find suitable sections with a coincidence condition.

Fig. 6 ist ein Querschnitt durch ein Absorptionselement 51 mit einem doppelrohrförmigen Koinzidenzwellenleiter 52. Im gasdicht abgeschlossenen Zwischenraum 53 befindet sich wieder Gas mit hoher Schallgeschwindigkeit.6 is a cross section through an absorption element 51 with a double tubular coincidence waveguide 52. In the gas-tight space 53 there is again gas with a high speed of sound.

Fig. 7 zeigt den Querschnitt eines Absorptionselementes 61 mit aus Honeycomb-Platten bestehenden Koinzidenzwellenleitern 62, die unter Bildung des Zwischenraumes 63 gasdicht zusammengefügt sind. Zweckmäßigerweise haben die zum Zwischenraum 63 hin orientierten Deckplatten öffnungen 64, so daß ein relativ großes Volumen im Zwischenraum 63 gebildet wird. In diesem Fall kann anstelle eines Gases mit hoher Schallgeschwindigkeit auch Luft im Zwischenraum 63 vorgesehen werden.FIG. 7 shows the cross section of an absorption element 61 with coincidence waveguides 62 consisting of honeycomb plates, which are joined gas-tight to form the intermediate space 63. The cover plates oriented towards the intermediate space 63 expediently have openings 64, so that a relatively large volume is formed in the intermediate space 63. In this case, air can also be provided in the intermediate space 63 instead of a gas with a high speed of sound.

Während in den Ausführungsbeispielen nach Fig. 1 bis 7 jeweils Biegewellenleiter benützt wurden, sind in Fig. 8 bis -11 Membranwellenleiter zugrundegelegt.While bending waveguides were used in the exemplary embodiments according to FIGS. 1 to 7, membrane waveguides are used as the basis in FIGS. 8 to -11.

Fig. 8 stellt ein Absorptionselement 71 dar, dessen Koinzidenzwellenleiter 72 Membranwellen ausführt. Er wird aufgespannt durch eine Rückenschale 74. Der Raum 73 zwischen Koinzidenzwellenleiter 72 und Rückenschale 74 ist evakuiert oder teilevakuiert. Im letzteren Fall hat das Restgas (Wasserstoff, Helium) eine hohe Schallgeschwindigkeit. Die Unterdruckbelastung ergibt in dem Koinzidenzwellenleiter 72 eine Zugbelastung. Zugbelastung und Massenbelegung ergibt in an sich bekannter Weise eine frequenz unabhängige Membrangeschwindigkeit. Diese wird auf Koinzidenz mit dem Umgebungsmedium ausgelegt.8 shows an absorption element 71 whose coincidence waveguide 72 executes membrane waves. It is spanned by a back shell 74. The space 73 between the coincidence waveguide 72 and the back shell 74 is evacuated or partially evacuated. In the latter case, the residual gas (hydrogen, helium) has a high speed of sound. The vacuum load results in a tensile load in the coincidence waveguide 72. The tensile load and mass assignment result in a frequency-independent membrane speed in a manner known per se. This is designed for coincidence with the surrounding medium.

Da die Druckbelastung des Koinzidenzwellenleiters 72 eine Krümmung ergibt, ist es vorteilhaft, eine solche Konstruktion gleichzeitig als Umlenkelement in einem Krümmer einzusetzen.Since the pressure load on the coincidence waveguide 72 results in a curvature, it is advantageous to use such a construction at the same time as a deflection element in a bend.

Bei einer Massenbelegung m der Membran, dem Druckunterschied ΔP. von Vorder- und Rückseite beträgt der Krümmungsradius r, der die Koinzidenzgeschwindigkeit c ergibt

Figure imgb0003
With a mass occupancy m of the membrane, the pressure difference ΔP. from the front and back is the radius of curvature r, which gives the coincidence speed c
Figure imgb0003

Fig. 9 stellt ein zu einem Rohr integrierten Absorptionselement 81 dar. Es besteht aus einem zylinderförmigen Koinzidenzwellenleiter 82, der durch einen Rohrmantel 84 gehalten ist. Der Raum 83 zwischen Koinzidenzwellenleiter 82 und Rohrmantel 84 ist voll- oder teilevakuiert. Dadurch besteht eine Spannung im Koinzidenzwellenleiter 82, die eine frequenzunabhängige Membranwellengeschwindigkeit ergibt. Dank der Querkontraktion setzen sich die primären Ringspannungen ebenfalls in Längsspannungen um, so daß die Membranwellengeschwindigkeit in beiden Richtungen gleich der Schallgeschwindigkeit des das Rohr durchströmenden Mediums gemacht werden kann.FIG. 9 shows an absorption element 81 integrated into a tube. It consists of a cylindrical coincidence waveguide 82 which is held by a tube jacket 84. The space 83 between the coincidence waveguide 82 and the tubular jacket 84 is fully or partially evacuated. As a result, there is a voltage in the coincidence waveguide 82, which results in a frequency-independent membrane wave velocity. Thanks to the transverse contraction, the primary ring stresses are also converted into longitudinal stresses, so that the membrane wave velocity can be made equal in both directions to the speed of sound of the medium flowing through the tube.

Fig. 10 stellt den zu Fig. 9 inversen Fall dar. Hier besteht das Absorptionselement 61 aus einem schlauchförmigen Koinzidenzwellenleiter 62. Dieser steht unter einem Innendruck P., wobei das Druckgas aus niedermolekularen Stoffen mit hoher Schallgeschwindigkeit besteht. Durch den Innendruck kann analog die Membranwellengeschwindigkeit auf Koinzidenz eingestellt werden.FIG. 10 shows the case inverse to FIG. 9. Here, the absorption element 61 consists of a tubular coincidence waveguide 62. This is at an internal pressure P., the compressed gas consisting of low molecular weight substances with high speed of sound. The membrane pressure can be set to coincidence by the internal pressure.

Fig. 11 zeigt ein zweiseitig wirkendes Absorptionselement 101, das an seinen Außenseiten gespannte Membrane als Koinzidenzwellenleiter 102 aufweist. Bei einer Membrandichte m [kg/m3] erhalten diese eine Spannung σ[N/m], so daß die Membrangeschwindigkeit

Figure imgb0004
gleich der Schallgeschwindigkeit des umgebenden Mediums, z. B. Luft ist. Die Spannung σ besteht in beiden Membranrichtungen, so daß Schall aus allen Winkelrichtungen absorbiert werden kann. In engen Kanälen mit einer Vorzugsrichtung genügt eine einachsige Membranspannung.FIG. 11 shows a double-acting absorption element 101, which has tensioned membranes on its outer sides as coincidence waveguides 102. With a membrane density of m [kg / m 3 ], they receive a tension σ [N / m], so that the membrane speed
Figure imgb0004
 equal to the speed of sound of the surrounding medium, e.g. B. is air. The tension σ exists in both diaphragm directions so that sound can be absorbed from all angles. A single-axis membrane tension is sufficient in narrow channels with a preferred direction.

Die Spannung selbst kann durch Federm 105 (z. B. Knickfedern) aufrechterhalten werden. Diese Federn 105 empfehlen sich besonders wegen ihrer Federkonstanz, so daß unabhängig von Dehnungen immer dieselbe Membranspannung aufrecht erhalten wird. Die Federn 105 selbst stützen sich auf eine Mittelplatte 104 ab. Der Innenraum 103 ist mit einem Gas großer Schallgeschwindigkeit erfüllt.The tension itself can be maintained by Federm 105 (e.g. buckling springs). These springs 105 are particularly recommended because of their spring constancy, so that the same membrane tension is always maintained regardless of expansions. The springs 105 itself based on a mean latte p 104.. The interior 103 is filled with a gas of high speed of sound.

Claims (8)

1. Absorptionselement mit geschlossener Oberfläche beruhend auf dem Koinzidenzeffekt, dadurch gekennzeichnet, daß je 2 Koinzidenzwellenleiter mit trapez-, wellen-, doppelwellen-oder rohrförmigem Profil bestehend aus einem Material mit hohen Elastizitätsmodul und geringer Dichte, z. B. Aluminium, Beryllium, CFK-, GFK-Fasern, Stahl zusammengefügt sind und der Zwischenraum gasdicht abgeschlossen und von einem Gas mit hoher Schallgeschwindigkeit, z. B. Wasserstoff oder Helium erfüllt ist und zur Fixierung Distanzhalter eingesetzt sind.1. absorption element with a closed surface based on the coincidence effect, characterized in that 2 coincidence waveguides each with a trapezoidal, wave, double-wave or tubular profile consisting of a material with a high modulus of elasticity and low density, for. As aluminum, beryllium, CFRP, GFRP fibers, steel are joined together and the space is sealed gas-tight and from a gas with high speed of sound, for. B. hydrogen or helium is met and spacers are used for fixation. 2. Absorptionselement nach Anspruch 1 dadurch gekennzeichnet, daß die Profiltiefe und damit deren Biegewellengeschwindigkeit der Koinzidenzwellenleiter in Querrichtung unterschiedlich ist (Fig. 4).2. Absorption element according to claim 1, characterized in that the profile depth and thus the bending wave speed of the coincidence waveguide is different in the transverse direction (Fig. 4). 3. Absorptionselement nach Anspruch 1 dadurch gekennzeichnet, daß die Profiltiefe der Koinzidenzwellenleiter in Längsrichtung unterschiedlich ist (Fig. 5).3. Absorption element according to claim 1, characterized in that the profile depth of the coincidence waveguide is different in the longitudinal direction (Fig. 5). 4. Absorptionselement nach den Ansprüchen 1 bis 3 dadurch gekennzeichnet, daß durch eine Querdehnung der Koinzidenzwellenleiter durch Bimetall-, Barometerfeder- oder gesteuerte mechanische Verstellung die Profilhöhe verändert und damit die Koinzidenzgeschwindigkeit einer wechselnden Betriebsbedingung'angepaßt wird (Fig. 3).4. Absorption element according to claims 1 to 3 characterized in that Barometerfeder- or controlled mechanical adjustment changed by a transverse expansion of the coincidence wave guide through bimetal, the profile height, and thus the coincidence rate of a changing operating condition adapted '(FIG. 3). 5. Absorptionselement nach dem Anspruch 1 dadurch gekennzeichnet, daß durch eine Zylinderschale (74) ein als Membranleiter wirkender Koinzidenzwellenleiter (72) aufgespannt ist dadurch, daß der sich bildende Zwischenraum (73) evakuiert bzw. bei Teilvakuum mit einem Gas hoher Schallgeschwindigkeit erfüllt ist.5. Absorbent element according to claim 1, characterized in that a coincidence waveguide (72) acting as a membrane conductor is spanned by a cylinder shell (74) in that the interstice (73) which is formed is evacuated or, in the case of partial vacuum, is satisfied with a gas of high speed of sound. 6. Absorptionselement nach dem Anspruch'1, dadurch gekennzeichnet, daß ein durch ein Rohr (84) aufgespannter zylinderförmiger Koinzidenzwellenleiter (82) als Membranleiter wirkt, wobei die Membranspannung durch Evakuieren des Zwischenraumes (8) bewerkstelligt wird.6. Absorption element according to claim ' 1, characterized in that a cylindrical coincidence waveguide (82) spanned by a tube (84) acts as a membrane conductor, the membrane tension being brought about by evacuating the intermediate space (8). 7. Absorptionselement nach dem Anspruch 1 dadurch gekennzeichnet, daß zwei Membranflächen (62) durch Federn unter Spannung gehalten werden, so daß deren Membranwellengeschwindigkeit auf Koinzidenz mit dem zu dämpfenden Umgebungsmedium eingestellt ist und gasdicht zusammengefügt sind, wobei der Zwischenraum mit einem Gas hoher Schallgeschwindigkeit erfüllt ist.7. Absorbent element according to claim 1, characterized in that two membrane surfaces (62) are held under tension by springs, so that their membrane shaft speed is set to coincide with the ambient medium to be damped and are joined gas-tight, the space being filled with a gas having a high speed of sound is. 8. Absorptionselement nach den Ansprüchen 1 bis 7, dadurch gekennzeichnet, daß die Koinzidenzwellenleiter durch Randdämpfung an den Rändern reflexionsfrei abgeschlossen sind.8. Absorption element according to claims 1 to 7, characterized in that the coincidence waveguides are finished reflection-free at the edges by edge attenuation.
EP81104147A 1980-06-02 1981-05-30 Sound absorbing element utilizing the effect of coincidence Expired EP0041260B1 (en)

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FR2691828A1 (en) * 1992-05-29 1993-12-03 Deutsche Aerospace Noise reduction device by acoustic short circuit.
FR2704969A1 (en) * 1993-05-06 1994-11-10 Centre Scient Tech Batiment Active double wall acoustic attenuation device
EP0710946A1 (en) * 1994-11-03 1996-05-08 Centre Scientifique Et Technique Du Batiment Double-walled active noise suppression device

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DE1572497A1 (en) * 1967-06-27 1970-02-19 Siemens Ag Sound insulation bodies, in particular for encapsulating machines
DE1803810A1 (en) * 1967-10-21 1969-06-12 Waertsilae Oy Ab Sound absorbers, especially for water pipes
DE2215083B2 (en) * 1972-03-28 1975-01-09 Max-Planck-Gesellschaft Zur Foerderung Der Wissenschaften E.V., 3400 Goettingen Fluid pipe line noise reducer - has a rigid rod base with varying shaped soft material filled recesses and flexible overcoat
DE2540518A1 (en) * 1974-09-16 1976-03-25 Bfg Glassgroup TRANSPARENT BOARD AND METHOD OF MANUFACTURING IT
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DE2531866A1 (en) * 1975-07-17 1977-01-20 Messerschmitt Boelkow Blohm Sound absorbing wall element - exploits coincidence effect of resonance with penetration velocity to damp surface waves
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DE2746061A1 (en) * 1977-10-13 1979-04-19 Rolf Jerke Heat and sound insulating panel - comprises hollow casing with evacuated interior supported against collapse by small dia. spacers
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DE2947026B1 (en) * 1979-11-22 1980-11-27 Messerschmitt Boelkow Blohm Silators for noise reduction

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2691828A1 (en) * 1992-05-29 1993-12-03 Deutsche Aerospace Noise reduction device by acoustic short circuit.
FR2704969A1 (en) * 1993-05-06 1994-11-10 Centre Scient Tech Batiment Active double wall acoustic attenuation device
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US5724432A (en) * 1993-05-06 1998-03-03 Centre Scientifigue Et Technique Du Batiment Acoustic attenuation device with active double wall
EP0710946A1 (en) * 1994-11-03 1996-05-08 Centre Scientifique Et Technique Du Batiment Double-walled active noise suppression device
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ATE9119T1 (en) 1984-09-15
DE3020830A1 (en) 1981-12-10

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