Patent EA-004974-B1 (EA)
Title: Acoustic device
Inventor: AZIMA HENRY
IPC: H04R1/00
Filed: 1996-09-02
Abstract: 1. Method of making an acoustic panel for radiating acoustic energy, the panel being capable of sustaining bending waves, the method comprising analysis of a distribution of resonant modes of bending wave vibration over a surface of the panel and selecting values of the panel parameters such as geometric size, panel stiffness, areal mass density and damping being beneficial to desired achievable acoustic operation over a frequency range of interest; and making the panel with the selected values of the parameters. 2. Method according to claim 1, wherein the panel parameters are associated with at least two different directions through the panel. 3. Method according to claim 1 or claim 2, wherein the analysis involves assessing the vibrational energy from the resonant modes in subareas of the surface of the panel; and the selecting is so as to reduce incidence of low vibrational energy in the subareas. 4. Method according to any preceding claim, wherein the selection of parameters is to provide a more even spread of vibrational energy over the surface of the panel. 5. Method according to any preceding claim, wherein the analysis involves assessing frequencies of the resonant modes, and the selecting is as to achieving optimum practical spacings of those frequencies. 6. Method according to any preceding claim, wherein the panel parameters are related to at least two different conceptual frequencies to which frequencies of the resonant modes can themselves be related. 7. Method of making an acoustic panel for radiating acoustic energy, the panel being capable of sustaining bending waves, the method comprising analysis of a distribution of resonant modes of bending wave vibration over a surface of the panel, the distribution being related to at least two conceptual frequencies that are dependent on values of at least two particular panel parameters to determine selected values of the panel parameters to give values of the conceptual frequencies thus related to the resonant modes at frequencies that are spaced and interleaved; and making a panel with the selected values of the panel parameters. 8. Method according to claim 6 or 7, comprising selecting panel parameters to provide conceptual frequencies that are related so that there is interleaving of the resonant mode frequencies with spacings at or approaching optimum for non-coincidence of the frequencies and evenness of the spacings. 9. Method according to any one of claims 6 to 8, comprising selecting the parameters to define the conceptual frequencies. 10. Method according to any preceding claim, comprising selecting panel parameters relating to geometrical configuration or shape and/or bending stiffnesses in different directions. 11. Method according to any preceding claim, comprising selecting panel parameters which are of a similar nature and which are selectable by a mutually relative value, such as a ratio or a relative percentage. 12. Method according to claim 10 or 11, comprising selecting geometrical parameters defining shape of at least the surface of the panel for given bending stiffness(es) of the panel. 13. Method according to claim 12, comprising selecting geometrical parameters which specify a particular variation of a basic shape according to dimensions in different directions across the shape. 14. Method of making an acoustic panel for radiating acoustic energy, the panel being capable of sustaining bending waves, the method comprising analysis of a distribution of resonant modes of bending wave vibration over a surface of the panel to determine values of geometrical parameters in respective ones of two directions across the panel that contribute with corresponding bending stiffnesses of the panel to deriving conceptual frequencies relatable to bending wave vibration of the panel being as useful for achievable acoustical action relative to desired performance, determining corresponding bending stiffnesses in the directions, and defining the panel by way of means limiting passage of bending waves beyond the limiting means; and making a panel bounded by the bending wave limiting means. 15. Method according to any preceding claim, comprising analysing resonant modes that are low in the frequency range. 16. Method according to claim 15, comprising analysing more than the first twenty resonant modes above the fundamental frequency of the panel. 17. Method according to claim 16, comprising analysing the first twenty-five or more resonant modes above the fundamental frequency. 18. Method according to any preceding claim, comprising selectively applying damping means to the panel to control frequencies corresponding to one or more of the resonant modes. 19. Method according to claim 18, comprising selectively applying damping means at medial positions of the panel. 20. Method of making an acoustic panel according to any preceding claim, comprising providing a device having a panel-form component and arranging at least a part of the component as the acoustic panel. 21. Method according to any preceding claim, comprising mounting a frame about the edge of the panel to permit bending wave vibration thereat to a desired extent. 22. Method according to claim 21, comprising mounting the frame with wave attenuating means between the frame and the radiator edges. 23. Method according to any one of claims 1 to 21, comprising defining the panel by means adversely affecting passage of bending waves beyond the panel. 24. Method according to any one of claims 1 to 23, comprising determining at least one location on the surface of the panel for locating a bending wave vibration transducer by first finding at least one region of the surface of the panel in which the high or highest numbers of resonant modes are present. 25. Method according to any one of claims 1 to 23, comprising determining two or more locations on the surface of the panel for locating bending wave vibration transducers by first finding regions in which in combination most or all of the resonant modes are present. 26. Acoustic panel obtainable by the method of any one of claims 1 to 23. 27. Acoustic panel according to claim 26, wherein the parameters are selected to provide interleaving of the resonant mode frequencies with spacings at or approaching optimum for non-coincidence of the modes and evenness of the spacings. 28. Acoustic panel according to claim 26 or 27, wherein the panel parameters define the conceptual frequencies. 29. Acoustic panel according to any one of claims 26 to 28, wherein the panel parameters relate to geometrical configuration or shape and/or to bending stiffnesses in different directions. 30. Acoustic panel according to any one of claims 26 to 29, wherein the panel parameters are of a similar nature and are selected by a mutually relative value, such as a ratio or a relative percentage. 31. Acoustic panel according to claim 29 or 30, wherein the panel parameters are geometrical and define the shape of the panel for given bending stiffness(es). 32. Acoustic panel obtainable by the method of any one of claims 1 to 23, comprising a panel capable of sustaining bending waves over its surface, the panel being of substantially rectangular shape with a first set of resonant modes relatable to a first conceptual frequency determined by the length of the panel and a second set of resonant modes relatable to a second conceptual frequency determined by the width of the panel, and a relationship between the conceptual frequencies such that lower frequency resonant modes arising from the conceptual frequencies are correlated by relating the first set of modes in the regions of the surface with more bending wave vibration activity with the second set of modes in the regions of the surface of less bending wave vibration activity. 33. Acoustic panel according to claim 32, wherein the substantially rectangular panel has substantially equal bending stiffnesses along its length and width, which are unequal dimensionally by about 13.4% or about 37%. 34. Acoustic panel according to claim 32 or claim 33, wherein one or more of the corners of the panel is cropped or trimmed or curved. 35. Acoustic panel according to claim 34, wherein the amount of cropping, trimming or curving of the corners is between about 10% and about 15%. 36. Acoustic panel according to claim 34 or claim 35, wherein the substantially rectangular panel has diagonal bending stiffness(es) different from bending stiffness(es) in the directions of its length and width. 37. Acoustic panel obtainable by the method of any one of claims 1 to 23, comprising a panel capable of sustaining bending waves over its surface, the panel being of substantially true elliptical shape with a first set of resonant modes relatable to a first conceptual frequency determined by its major axis and a second set of resonant modes relatable to a second conceptual frequency determined by its minor axis, and a relationship between the conceptual frequencies such that lower frequency resonant modes arising from the conceptual frequencies are correlated by relating the first set of modes in regions of the surface with more bending wave vibration activity with the second set of modes in regions of the surface of less bending wave vibration activity. 38. Acoustic panel according to claim 37, wherein the panel has substantially equal bending stiffnesses along its major and minor axes, which are dimensionally unequal by about 18.2% or about 34%. 39. Acoustic panel obtainable by the method of any one of claims 1 to 23, comprising a panel capable of sustaining bending waves over its surface, wherein the panel is of substantially super-elliptical shape defined by the equation (x/a)<2N> + (y/b)<2N>= 1 where a is the major axis, b is the minor axis and 2n is the super-ellipse defining power factor with a first set of resonant modes relatable to a first conceptual frequency determined by its major axis and a second set of resonant modes relatable to a second conceptua