ACOUSTIC CONSTRUCTION ELEMENT FOR SOUND INSULATION IN A BROAD RANGE OF FREQUENCIES

Abstract: The invention relates to an acoustic construction element comprising sound insulating cavities of which at least part have a first portion (4), which is situated closest to the external surface (3) of the element and at least a second portion (5) having a maximum internal width (6) which is larger than the smallest width of said first portion (4) of the cavity. At least some of said cavities have different internal volume, of which preferably the portion of the cavities beyond the first portion have a circular or oval shape. Said construction element further comprises preferably cavities (e, f, h) having a substantially constant width over their entire depth. The invention further relates to the use and the method of manufacturing said construction elements.

Description: ACOUSTIC CONSTRUCTION ELEMENT FOR SOUND INSULATION IN A BROAD RANGE OF FREQUENCIES The present invention relates to an acoustic construction element comprising sound insulating cavities . The use of the "mass" of a construction element and/or perforations or cavities made in a construction element to obtain sound-insulation is a common known principle. In European patent application n° EP 0 580 096, for example, there is described a sound-insulation element having a wall, exhibiting perforations, and having a cavity which receives a sound-absorbing packing, which covers the mouths of the perforations. The perforation- containing wall is formed by a plurality (at least two) of acoustic bricks which are fastened one beside the other on a cross-sectionally U-shaped shell. The acoustic bricks usually consist of ceramic material . In French patent application n° FR 2612225, there is revealed an acoustic lining element, made of burnt clay, ceramic materials, cement, wood, plaster or the like. This acoustic lining element comprises a plane rectangular face intended to be attached to a wall . The opposite face to this one comprises a network of ribs forming corrugations parallel to one of the sides. The disadvantage of these acoustic construction elements is that they preferably need an addition of sound- insulating material to obtain the desired sound-absorbing properties . To become sufficient sound-insulation without the need of supplementary sound absorbing material, Japanese patent application n° JP 09328833 describes a sound-absorbing block by baking fire clay, into which a pore imparting material is mixed, and fire-resisting chamotte. In the ceramic block, there are bored holes of different depth, drilled all over at right angles to the thickness direction. The ceramic block is reported to have sound absorbing performance in a frequency band having broad width. The problem with this state of the art technique is that there still are sound frequencies that are not absorbed and thus can lead to noise pollution or disturbing noise. The object of this invention is to provide in a sound- insulating construction element that can absorb a broad range of sound frequencies and that can be manufactured depending on the type or the frequency of noise pressure. For instance, the frequency of the disturbing noise that results from a truck that drives on a highway differs from the noise that has to be absorbed when one records a song in a music studio. This object is achieved by an acoustic construction element comprising sound insulating cavities, but in which at least part of the cavities have a first portion (in particular the access part to the cavity) , which is situated closest to the external surface of the element and at least a second portion having a maximal internal width which is larger than the smallest width of said first portion of the cavity. In a preferred embodiment, at least some of said cavities have different internal volumes. This makes it possible to absorb a wide range of different sound frequencies. A further characteristic of the invention is that the cavities have a constant shape along an axis parallel to the exposed surface of the construction element in use. The cavities can have different shapes . In a first embodiment of the invention, the portion of the cavities beyond the first portion is circular or oval in shape . In an other preferred embodiment, said construction element further comprises cavities having a substantially constant width over their entire depth. Preferably, at least some of said further cavities have different internal depths. The construction element can be manufactured out of different materials. Preferably, said construction element is made of ceramic material. In this way, ceramic construction elements can be used as regular building bricks. An advantage not to neglect is that the construction element according to the invention can be used as a load carrying construction element . The method for manufacturing acoustic construction elements is preferably by way of extrusion of the ceramic materials . Further distinctive features and characteristics will be clarified in the following description of a specific embodiment of the invention as respresented in the attached drawings. It should be noted that this embodiment is only given by way of example and implies no restriction in het general scope of the invention as that apppears from the above description and from the claims at the end of this text . In the attached drawings : figure 2 is a perspective side and front view of an acoustic construction element according to the invention; - figure 2 is a side view of an acoustic construction element as shown in figure 1 . As shown in figure 1, the acoustic construction element is an acoustic brick (1) with a length (L) of 324 cm, a heigth (H) of 5 cm and a width (W) of 10 cm. The brick is manufactured by extrusion of ceramic material, more specific red-baking clay. The acoustic brick has a smooth surface. By using other clays or by addition of aggregates to the base material, the brick can obtain a different color or even a sandy structure . The surface can also be rough. In function of the composition, characteristics as the absorption of water, the intensity of the pressure,... can differ. As shown at figure 2, the acoustic brick comprises at irregular distances, varying between 1 and 4 centimeter, separate entries of cavities (4) . At least part of said cavities have a first portion (4) , which is situated closest to the external surface of the element and at least a second portion (5) having a maximum internal width (6) which is larger than the smallest access to the cavity. In the example, the cavities are each characterised by an elongated (of type e, f or h) or a "circular" (of type g, i) cavity with a different width, depth or circular shape. Herewith, an aimed distribution of different sound-absorbing and/or reflection-rooms is achieved, through which sound with varying frequencies can be muffled and absorbed. Typical of the elongated cavities are the width of the cavity (w e ) and the depth (d e ) in the ceramic mass. Typical of the circular cavities are the width of the access or entry at the top of the cavity (w c ) , but especially the radius (r c ) and the depth (d c ) of the centre (x) of the circle. Instead of a circular shaped cavity, the cavity can also be oval shaped (cfr. cavity type i) . The brick has thus a two-fold function: for one, the ceramic mass takes care for the absorption of the sound, and for another, the cavities are dimensioned in such a way that by the way of internal reflection, the sound doesn't get the chance to be reflected into free space. In this way, the width ( ) of the stone and the width (w c , w e ) , the depth (d c , d e ) , the radius (r c ) of the cavities and their position on the stone can be adapte in function of certain types of frequencies and/or the level of the sound that has to be adsorbed. Once the character is known of the disturbing sound, the perforation pattern and the width of the stone can be laid down. It is a purpose that said perforation pattern is repetitive. That's why the upper ends (2) are rounded off, with the purpose that the joining creates a new cavity. The cavities have a constant shape along an axis parallel to the exposed surface of the acoustic brick in use (= along the heigth (H) of the acoustic brick) . The acoustic construction element according to the invention can be used on every place where noise or noise pollution is an item, for instance in: laboratory - hospitals - industry: * as an inside or outside wall of factories, offices, * around compressors, motors, machines and computer rooms - concert halls, theatres, disco's, exposition halls, cinema rooms, hotel and catering industry, ... along motorways, highways, train sections, stations, airports, ... as a partition wall in apartment buildings and office buildings: around elevator shafts, engine rooms, ... - municipal buildings: libraries, sport halls, cultural centers, schools and universities agriculture and cattle breeding: pig farms, chicken coops , ... In certain applications, the cavities can also serve as a carrier of technical pipes for for instance electricity, computers, telephone, sanitary, heating, .... The bricks or the panels can be mounted either horizontally, either vertically, or in a combination of the two, can be glued together or layed in bricks, or can function as a carrying or non-carrying part. For example, the bricks can be used as road blocks on which traffic can circulate. The disturbing frequencies that arise when car tyres roll over the road surface can be absorbed by using the acoustic bricks as horizontal carrying driving surfaces. The cavities that are present in the bricks could also function for draining the excess of water when it's raining.

Claims: C L A I S 1. Acoustic construction element comprising sound insulating cavities characterised in that at least part of said cavities have a first portion (4) , which is situated closest to the external surface (3) of the element and at least a second portion (5) having a maximum internal width (6) which is larger than the smallest width of said first portion (4) of the cavity. 2. Acoustic construction element according to claim 1 characterised in that at least some of said cavities have different internal volumes. 3. Acoustic construction element according to claim 1 or 2 characterised in that the cavities have a constant shape along an axis parallel to the exposed surface of the construction element in use. 4. Acoustic construction element according to one of claims 1 to 3 characterised in that the portion of the cavities beyond the first portion is circular or oval in shape. 5. Acoustic construction element according to any one of claims 1 to 4 characterised in that said construction element further comprises cavities (e, f, h) having a substantially constant width over their entire depth. 6. Acoustic construction element according to claim 5 characterised in that at least some of said further cavities (e, f, h) have different internal depths. 7. Acoustic construction element according to any one of claims 1 to 6 characterised in that said construction element is made of ceramic material. 8. Use of an acoustic construction element as a load carrying construction element. 9. Use of an acoustic construction element according to claim 8 characterised in that a construction element according to any one of claims 1 to 6 is used. 10. Method for manufacturing acoustic construction elements characterised in that the shape of said construction elements results from the extrusion of ceramic material . 11. Method according to claim 10 characterised in that cavities are extruded according to any one of claims 1 to 6.

Inventors: VAN REETH RUDY, WAGENER FONS, VAN REETH, RUDY, WAGENER, FONS
Applicants: REETH RUDY VAN, TERCA BRICKS N V, WAGENER FONS, TERCA BRICKS N.V., VAN REETH, RUDY, WAGENER, FONS
Application year: 2000
Main classification: E01F8
IPC codes: E01F8