# US 5,706,254 A · Surface element and a device for generating sound > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,706,254 A - Document ID: US5706254A - Status: Granted - Kind: A - Application number: 08/737,762 - Filed: 1996-11-18 - Granted: 1998-01-06 - Earliest claimed: 1994-05-19 - Inventors: Lars Stahl - Web page: https://patentgrep.com/patent/US5706254A ## CPC - H04R 15/00: Magnetostrictive transducers (magnetostrictive elements in general H10N30/00) - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) ## Abstract A surface element for a device for generating sounds by influencing opposite extremities of a surface element to oscillate from and towards each other and thereby the surface element to oscillate transversely thereto and generate sounds has at least a portion formed in the thickness direction thereof by at least two first layers (12) and an intermediate layer (13) having a lower average density than the density of the two first layers. ## Claims ### Claim 1 A surface element for a device for generating sound by influencing opposite ends (8, 9) of the surface element to oscillate from and towards each other, thereby making the surface element oscillate transversely thereto and generate sound, characterized in that at least a portion thereof is formed in the thickness direction thereof by at least two first layers (12, 12') and an intermediate layer (13, 13') having a lower average density than the density of the two first layers. ### Claim 2 (depends on 1) A surface element according to claim 1, characterized in that its centre region between said ends is light in relation to the rest of the surface element. ### Claim 3 (depends on 2) A surface element according to claim 2, characterized in that its transmission ratio in the centre region is high. ### Claim 4 (depends on 3) A surface element according to claim 3, characterized in that said transmission ratio is higher than 6, preferably higher than 8. ### Claim 5 (depends on 2, 3, 4) A surface element according to any of the claims 2-4, characterized in that said centre region is a centrally located region of the surface element which substantially is located within a limited area, the boundaries of which has a distance to each end of at least 1/5 of the distance between said ends. ### Claim 6 (depends on 5) A surface element according to claim 5, characterized in that said distance is at least 1/4. ### Claim 7 (depends on 2) A surface element according to any of claims 2, characterized in that said at least one portion having at least two first layers (12, 12') and in intermediate layer (13, 13') is arranged in said centre region and forms at least 10% of the total area of the surface element. ### Claim 8 (depends on 7) A surface element according to claim 7, characterized in that said at least one portion forms at least 20%, preferably at least 30%, of the total area of the surface element. ### Claim 9 (depends on 8) A surface element according to claim 8, characterized in that said at least one portion forms generally 50% of the total area of the surface element. ### Claim 10 (depends on 1) A surface element according to claim 1, characterized in that the major part thereof is formed by one or more of said portions having at least two first layers (12, 12') and an intermediate layer (13, 13'). ### Claim 11 (depends on 1) A surface element according to any of claims 1, characterized in that the two first layers (12) adjoin at at least one location (14) under disappearance of the intermediate layer, in order to form a so called hinge at said location through a reduction of rigidness of the surface element obtained through said adjoining. ### Claim 12 (depends on 11) A surface element according to claim 11, characterized in that it is provided with such a location (14) for adjoining of the two first layers (12) in the neighbourhood of at least one of said ends (8, 9) of the surface element. ### Claim 13 (depends on 1) A surface element according to any of claims 1, characterized in that the intermediate layer (13) presents at least one swelling (15) for local increase of the rigidity of the element. ### Claim 14 (depends on 1) A surface element according to any of claims 1, characterized in that the intermediate layer (13, 13') is homogenous. ### Claim 15 (depends on 1) A surface element according to any of claims 1, characterized in that the intermediate layer (13) comprises cavities (17). ### Claim 16 (depends on 14) A surface element according to claim 14, characterized in that at least one bridge (15) which connects the two first layers (12) extends through the intermediate layer (13). ### Claim 17 (depends on 16) A surface element according to claim 16, characterized in that said bridge is formed by the same material as said first layer. ### Claim 18 (depends on 16) A surface element according to claim 16, characterized in that said bridge (15) has a beam-like character and a longitudinal direction which goes generally in the direction from one of the ends (8, 9) of the surface element to the other end thereof. ### Claim 19 (depends on 1) A surface element according to any of claims 1, characterized in that it comprises at least one portion (16) with more than two first layers (12, 12') and, between each first layer respectively, intermediate layers (13, 13') having a lower average density than the density of said first layers. ### Claim 20 (depends on 2) A surface element according to claim 2, characterized in that it presents at least one portion having at least two first layers (12) and one said intermediate layer (13) only in the centre region between said ends of the surface elements. ### Claim 21 (depends on 1) A surface element according to any of claims 1, characterized in that said first layer (12) has a varying thickness. ### Claim 22 (depends on 21) A surface element according to claim 21, characterized in that the thickness of the first layers (12) increases in the direction towards each of said ends (8, 9) respectively of the surface element. ### Claim 23 (depends on 1) A surface element according to any of claims 1, characterized in that said first layer (12, 12') is made of a material with a low density. ### Claim 24 (depends on 1) A surface element according to any of claims 1, characterized in that a material with high elasticity module is a part of said first layer (12, 12'). ### Claim 25 (depends on 23) A surface element according to claim 23, characterized in that the density of the material of said first layer (12, 12') is less than 2 200 kg/m.sup.3. ### Claim 26 (depends on 24) A surface element according to claim 24, characterized in that the elasticity module of a material comprised in said first layer (12, 12') is higher than 1,5.times.10.sup.5 MPa. ### Claim 27 (depends on 1) A surface element according to any of claims 1, characterized in that the average density of the intermediate layer (13, 13') is substantially lower than the density of the material of said first layer (12, 12'). ### Claim 28 (depends on 27) A surface element according to claim 27, characterized in that the average density of the intermediate layer (13, 13') is less than a quarter of the density of the material of said first layer (12, 12'). ### Claim 29 (depends on 1) A surface element according to any of claims 1, characterized in that said intermediate layer (13, 13') is at least partly formed by a material having a low elasticity module. ### Claim 30 (depends on 1) A surface element according to any of claims 1, characterized in that the first layers (12, 12') are formed by fibre composite material. ### Claim 31 (depends on 1) A surface element according to any of claims 1, characterized in that it is arranged to be used for the generation of sound in air. ### Claim 32 A device for generating sound, which comprises a surface element (5) in which two opposite ends (8, 9) are intended to be connected to a piece (6) each, and a driving unit (7) arranged to influence said pieces and thereby the ends of the surface element to oscillate from and towards each other and thereby the surface element to oscillate transversely thereto and generate sound, characterized in that at least one portion of said surface element is formed in the thickness direction thereof by two first layers (12, 12') and an intermediate layer (13, 13') with a lower average density than the density of said two first layers.