Patent Publication Number: US-6705426-B2

Title: Acoustic diffuser and method of production

Description:
FIELD OF THE INVENTION 
     The invention concerns an acoustic diffuser, ovaloid, ellipsoid or spheroid in shape, made in a monocoque so as to eliminate the acoustic reflections, refractions and vibrations which damage the quality of the sound. 
     The invention also concerns the method to produce said acoustic diffuser. 
     BACKGROUND OF THE INVENTION 
     The state of the art includes acoustic diffusers having containers composed of at least two semi-coques made of plastic material, plywood or composite materials, attached together and with a substantially box-like shape. 
     Such diffusers usually comprise at least a loudspeaker able to broadcast the sound, possibly associated with a printed circuit able to support an electric-acoustic filter, for example of the crossover type, an electric connector, for example of the jack type. 
     Acoustic diffusers made in this way create vibrations, reverberations, or other distortions inside, which affect the quality of the sound. 
     The present Applicant has devised and embodied this invention to overcome this shortcoming of the state of the art, and to obtain further advantages. 
     SUMMARY OF THE INVENTION 
     The invention is set forth and characterized essentially in the main claims, while the dependent claims describe other innovative characteristics of the invention. 
     One purpose of the invention is to achieve an acoustic diffuser which will prevent the formation of echoes, reverberations or vibrations inside it, and of refractions in the emission of sound. 
     Another purpose of the invention is to achieve an acoustic diffuser which is attached so as to limit the diffusion or transmission of contact vibrations, and which can be installed easily, and positioned at different heights, and directed at an angle in space. 
     Another purpose is to perfect a method which will allow to make a monocoque acoustic diffuser in a simple and efficient manner. 
     In accordance with these purposes the acoustic diffuser according to the invention comprises a containing element formed by a monocoque and at least a loudspeaker. 
     The monocoque is made from a compound of solid mineral aggregates, for example silicon, basalt and quartz, and a cohesion material, such as for example an epoxy resin, so as to limit the vibrations and to ensure a high structural density in order to optimize the frequency of resonance. The monocoque is substantially rounded in shape, such as for example ovaloid, ellipsoid or spheroid, in order to eliminate acoustic reflections and the formation of reverberations inside it. 
     The acoustic diffuser comprises, in one embodiment, an outer covering shell composed by an abradable resin, and an inner shell formed by plastic material. The two shells follow the outer, respectively inner, profile of the monocoque and provide the through holes able to house the loudspeaker and/or any other electric and electronic components such as, for example, connectors, pre-printed circuits, or for acoustic devices such as for example vents to allow the air, put under pressure by the movement of the loudspeaker, to exit from the containing element. 
     The acoustic diffuser also comprises support means which allow it to be fixed from above to at least one surface; in this case, they are formed by a steel cable which is inserted into a cavity of the containing element and a shock absorber element inserted between one end of the steel cable and the containing element, so as not to transmit the possible vibrations of the containing element to the surface. 
     The acoustic diffuser as described heretofore is made according to the following method. 
     The containing element is formed by inserting solid mineral aggregates, for example with a high level of hardness with a granulometry varying from about 1 mm to about 5 mm, inside a mold and the subsequent casting, or insertion under pressure, of a cohesion material into the same mold, so that the resulting containing element consists of a monocoque. 
     The mold has a substantially rounded inner surface, such as for example ellipsoid, ovaloid or similar, and is formed by two substantially symmetrical half-molds. 
     An inner shell is positioned inside the mold, so as to define an interspace inside which the granules and the cohesion material are cast. 
     In one embodiment, an outer shell is shaped on the inner surface of the mold, so as to form, together with the inner shell, an interspace inside which the granules of hard mineral, and subsequently the cohesion material, will be inserted. 
     Once the cohesion material has solidified, the two half-molds are removed and the surface finishing of the monocoque, or of the outer shell, is done, the loudspeaker is assembled, and any other possible electric and electronic components or acoustic devices provided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other characteristics of the invention will be apparent from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached drawings wherein: 
     FIG. 1 is a sectioned side view of the acoustic diffuser according to the invention; 
     FIG. 2 is a sectioned side view of the molding of the acoustic diffuser shown in FIG. 1; 
     FIG. 3 shows a variant of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     With reference to FIG. 1, the acoustic diffuser  10  according to the invention is substantially formed by a containing element  11  and a loudspeaker  12 . 
     The containing element  11  is substantially ovaloid in shape, and is formed by a monocoque  11   a  made of a compound of granules of solid mineral such as, for example silicon and basalt, and a cohesion material such as for example an epoxy resin. The function of the compound is to raise the frequency of resonance with a dense and compact mass, of considerable weight, in the order of about 7 Kg, for a good physical-environmental balance, and to limit vibrations; the purpose of its shape is to eliminate the acoustic reflections and the formation of reverberations inside it. 
     The containing element  11  comprises an outer shell  13 , made in this case from an abradable resin, disposed on the outer surface of the monocoque  11   a , and an inner shell  14  formed by two half-shells  14   a  and  14   b , advantageously made of plastic material, disposed on opposite sides of the inner surface of the monocoque  11   a.    
     The outer shell  13  substantially comprises a hole  15   a  to house the loudspeaker  12  and to position a holed protection grid  36 , of a conventional type, a hole  21   b  to allow the compound which constitutes the monocoque  11   a  to be cast, and a tubular recess  16   a  to allow the air moved by the action of the loudspeaker  12  to exit from the containing element  11 . 
     The inner half-shell  14   a  comprises a hole  15   b  disposed, during use, in correspondence with the hole  15   a  of the outer shell  13  and, in the upper part, a plane portion  18   a  able to allow a bushing  22  to be housed. 
     The inner half-shell  14   b  comprises three holes  19  to house respective screws  20 , a hole  16   b  disposed, during use, in correspondence with the tubular recess  16   a  of the outer shell  13 , and able to be associated by means of glues with a tube  23 , at least as long as the tubular recess  16   a ; moreover, the half-shell  14   b  comprises a through hole  24   a  able to couple with a mating connector support  25 , advantageously made of stainless steel, and a plane portion  18   b  disposed during use as an extension of the corresponding plane portion  18   a.  The loudspeaker  12  is attached to the containing element  11  by means of a ring nut  17 , advantageously made of stainless steel, attached to the half-shell  14   a  in correspondence with the hole  15   b , while a printed circuit  26  for acoustic filters  27  of the crossover type is attached to the screws  20 . 
     Finally, the bushing  22  is buried inside the monocoque  11   a , in correspondence with the plane portions  18   a  and  18   b , and a cable  28  is attached thereto by means of a dowel screw  29 . The cable  28  is inserted longitudinally with play into the dowel screw  29  and comprises an abutment element or stopper  31  at one end, on which a bellows-shaped rubber  30  rests; during use, the rubber  30  is able to position itself between the stopper  31  and the dowel screw  29 , absorbing any possible vibrations and movements of the containing element  11 . 
     In order to make the acoustic diffuser  10  a mold  32  is used, formed by two half-molds  32   a  and  32   b  having respective inner surfaces  33   a  and  33   b  shaped so that, during use, they define a substantially ovaloid shape on which the outer shell  13  is shaped. 
     The half-mold  32   a  comprises a hole  15   c  able to house a metal mask  15  forming the shaped hole  15   a  of the outer shell  13 , and to support, distancing it, the inner half-shell  14   a , by means of attachment screws (not shown in the drawings). 
     The half-mold  32   b , on the contrary, comprises a hole  21  disposed, during use, in correspondence with the hole  21   b  which allows the compound to be cast, a seating  16   c  able to house a second metal mask  16  able to define the tubular recess  16   a,  and finally a last hole  24  allows to insert the connector support  25  into the hole  24   a.    
     After shaping the shell  13  respectively to the surfaces  33   a  and  33   b , after positioning the two half-shells  14   a  and  14   b  inside the mold  32 , after arranging the screws  20  in the relative holes  19 , after inserting the connector support  25  into the hole  24   a,  and after positioning the bushing  22  above the plane portions  18   a  and  18   b , the two half-shells  14   a  and  14   b  are reciprocally attached by means of glues so as to form the shell  14 . 
     A structure is created by attaching the two half-molds  32   a  and  32   b  together, with inside the shell  13  and the inner shell  14  so that they form an interspace. The masks  15  and  16  are inserted, the tubular recess  16   a  is blocked with a stopper  34  and then the granules of solid mineral are inserted, simultaneously shaking the structure formed, in such a manner that the granules penetrate inside the whole interspace. 
     The subsequent step includes the pouring of the cohesion material, either under pressure or in a cast, until there is a slight overflow from the hole  21   b  or from possible vents. 
     After the cohesion material has solidified, the two half-molds  32   a  and  32   b  are dis-associated, and the loudspeaker  12 , the printed circuit  26 , a connector  25   b  and the cable  28  are assembled and electrically connected; it is also possible to line the inner part of the inner shell  14  with soundproofing material. There then follows the step of surface finishing, with sanding and painting of the outer surface of the shell  13 . 
     Once assembled, the acoustic diffuser  10  communicates with the outside only by means of the tubular recess  16   a , since all the other apertures are air tight. 
     According to a variant shown in FIG. 3, the tubular recess  16   a  is replaced by a wall  35 , substantially parallel to the half-shell  14   a,  and open in proximity with the hole  15   a  of the shell  13 . 
     According to another variant, not shown in the drawings, two bushings  22  are disposed on opposite sides so as to allow the containing element  11  to be attached to two opposite surfaces, in order to prevent it from oscillating. 
     It is clear however that modifications and/or additions can be made to the acoustic diffuser  10  and its method of production as described heretofore without departing from the spirit and scope of the invention. 
     For example, the solid material which makes up the monocoque  11   a  of the containing element  11  can consist of a metal such as aluminium, steel or otherwise. 
     It is also clear that, although the invention has been described with reference to specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of acoustic diffuser and its production method, all of which shall come within the field and scope of this invention.