초록 ▼

A room acoustic diffuser exploits interference, by reflecting waves out-of-phase with the specular energy, making it possible to diminish specular energy. This is achieved by using a diffuser based on a ternary sequence, which nominally has reflection coefficients of 0,-1 and +1. A method for obtain

A room acoustic diffuser exploits interference, by reflecting waves out-of-phase with the specular energy, making it possible to diminish specular energy. This is achieved by using a diffuser based on a ternary sequence, which nominally has reflection coefficients of 0,-1 and +1. A method for obtaining the design sequence for Quaternary diffusers is also disclosed. Also, design methods for forming the sequences into arrays, and forming hemispherical diffusers are explained.

대표청구항 ▼

The invention claimed is: 1. A hybrid amplitude-phase grating diffuser comprising: a) a forward facing surface including: i) a first plurality of absorbent patches; and ii) a second plurality of reflective patches; b) said diffuser further including a reflective well; c) said absorbent patches, re

The invention claimed is: 1. A hybrid amplitude-phase grating diffuser comprising: a) a forward facing surface including: i) a first plurality of absorbent patches; and ii) a second plurality of reflective patches; b) said diffuser further including a reflective well; c) said absorbent patches, reflective patches and reflective well combining together to form a variable impedance surface having pressure reflection coefficients of 0, 1 and-1, respectively. 2. The diffuser of claim 1, wherein said first plurality of absorbent patches and second plurality of reflective patches all have zero depth. 3. The diffuser of claim 2, wherein said reflective well has a depth comprising one-quarter of a wavelength at a design frequency of said diffuser. 4. The diffuser of claim 3, wherein said absorbent patches, reflective patches, and reflective well are arranged in a random or pseudo-random sequence, whereby sound scattered in a specular direction is suppressed by attenuation of the absorbent patches and destructive interference between said reflective patches and reflective well. 5. The diffuser of claim 4, wherein said absorbent and reflective patches are arranged in a ternary sequence, whereby sound scattered in a specular direction is suppressed by attenuation of the absorbent patches and destructive interference between said reflective patches and reflective well, more effectively than would be the case were the patches and well arranged in a random or pseudo-random sequence. 6. The diffuser of claim 5, wherein said ternary sequence is computer optimized to comprise the sequence 1 1 0 1 0 0-1, where "1" signifies one of said absorbent patches, "0" signifies one of said reflective patches, and "1" signifies said reflective well. 7. The diffuser of claim 1, wherein said well comprises a plurality of wells, each having a depth of a quarter wavelength at a design frequency of said diffuser. 8. The diffuser of claim 5, wherein said ternary sequence comprises a 31 element correlation identity derived ternary sequence 0 0 1 1-1 1-1 0 0 0 1 1 0 1-1-1 0 1 0-1 0 0 0 0-1 0 0 1 0 1, where "0" signifies one of said absorbent patches, "1" signifies one of said reflective patches, and "-1" signifies said reflective well. 9. The diffuser of claim 8, further including means for scattering sound in a single plane. 10. The diffuser of claim 9, wherein said means for scattering sound comprises linear adjacent strips. 11. A hybrid amplitude-phase grating diffuser comprising: (a) a forward facing surface including: (i) a first plurality of absorbent patches; and (ii) a second plurality of reflective patches; (b) said diffuser including a first reflective well having a first depth comprising a quarter wavelength at a design frequency of said diffuser; (c) said diffuser further including a second reflective well having a second depth related to said first depth by a relationship chosen from the group consisting of (1) a fraction defined by a reciprocal of a prime number, (2) a rational fraction, and (3) a number theoretical phase grating, thereby ensuring that no sound waves reflecting from non-absorbing portions of said diffuser are in phase within an audible frequency range. 12. The diffuser of claim 11, wherein said absorbent patches, reflective patches, first reflective well and second reflective well combine together to form an impedance surface having pressure reflection coefficients of 0, 1,-1 and i, respectively. 13. The diffuser of claim 11, wherein said first reflective well comprises a plurality of wells with a first equal depth and said second reflective well comprises a plurality of wells with a second equal depth different from said first equal depth. 14. The diffuser of claim 11, wherein said patches are arranged according to a Quaternary sequence, with said first and second reflective wells providing destructive sound interference at odd and even multiples of said design frequency, respectively. 15. The diffuser of claim 11, wherein said first plurality of absorbent patches subtends up to 50% of a total area of said forwarding facing surface. 16. The diffuser of claim 6, 8 or 11, wherein a transition from absorption to diffusion occurs at about 1-2 kHz. 17. The diffuser of claim 6, 8 or 11, wherein said reflective well has a surface parallel to said forward facing surface. 18. The diffuser of claim 6, 8 or 11, wherein said reflective well has a surface angled with respect to said forward facing surface. 19. The diffuser of claim 6, 8 or 11, wherein said reflective well includes surfaces defining an "L" shaped chamber folded well. 20. The diffuser of claim 6, 8 or 11, wherein said diffuser comprises a first diffuser and a second diffuser. 21. The diffuser of claim 20, wherein said first diffuser has patches and a well arranged in a first ternary sequence and said second diffuser has patches and a well arranged in a second ternary sequence. 22. The diffuser of claim 21, wherein said second ternary sequence is inverted with respect to said first ternary sequence. 23. The diffuser of claim 22, comprising a relatively large modulated diffuser composed of said first and second diffusers arranged according to an optimal binary sequence in which a zero of said sequence refers to said first ternary sequence and a one of said sequence refers to said second inverted ternary sequence, thereby forming an aperiodic array using two base shapes. 24. The diffuser of claim 21, wherein said second ternary sequence is reversed with respect to said first ternary sequence. 25. The diffuser of claim 24, comprising a relatively large modulated diffuser composed of said first and second diffusers arranged according to an optimal binary sequence in which a zero of said sequence refers to said first ternary sequence and a one of said sequence refers to said second reversed ternary sequence, thereby forming an aperiodic array using a single base shape. 26. The diffuser of claim 20, wherein said patches and well of said first diffuser are arranged in a sequence 1 1 0 1 0 0-1, where "1" signifies one of said absorbent patches, "0" signifies one of said reflective patches, and "-1" signifies said reflective well. 27. The diffuser of claim 20, wherein said patches and well of said second diffuser are arranged in a sequence-1-1 0-1 0 0 1, where "-1" signifies one of said absorbent patches, "0" signifies one of said reflective patches, and "1" signifies said reflective well. 28. The diffuser of claim 20, wherein said patches and well of said second diffuser are arranged in a sequence-1 0 0 1 0 1 1, where "-1" signifies one of said absorbent patches, "0" signifies one of said reflective patches, and "1" signifies said reflective well. 29. A ternary diffuser comprising: a) a forward facing surface including: i) a first area of absorbent patch subtending up to 50% of a total area of said surface; and ii) a second area of reflective patch; b) said diffuser further including a reflective well; c) said patches and well being arranged in a ternary sequence, whereby sound directed at said diffuser is scattered with a specular lobe of said sound being suppressed. 30. The diffuser of claim 29, wherein a transition from absorption to diffusion occurs at about 1-2 KHz. 31. The diffuser of claim 29, wherein distribution of locations of said areas and well is chosen at random. 32. The diffuser of claim 29, wherein distribution of said areas and well is chosen using optimization techniques for short sequences, and ternary and quaternary sequences for longer sequences. 33. The diffuser of claim 29, wherein said well comprises a plurality of wells. 34. The diffuser of claim 29, wherein said wells have depths chosen from the group consisting of (1) a constant quarter wavelength depth, (2) a series of depths related by fractions consisting of reciprocals of prime numbers or rationals, of a quarter wavelength well depth, and (3) a series of depths derived from a number theoretic phase grating. 35. The diffuser of claim 29, including means for scattering sound in a single plane. 36. The diffuser of claim 35, wherein said means for scattering comprises linear adjacent strips. 37. The diffuser of claim 35, wherein said means for scattering operates hemispherically with two-dimensional arrays of absorptive, reflective and quarter wave deep areas. 38. The diffuser of claim 29, wherein said well has a surface parallel to said forward facing surface. 39. The diffuser of claim 29, wherein said well has a surface angled with respect to said forward facing surface. 40. The diffuser of claim 29, wherein said well has a surface defining an L-shaped chamber. 41. A hemispherically-scattering, hybrid, ternary diffuser array comprising: a) a forward facing 2-dimensional array surface including: i) a first area of absorbent patch subtending up to 50% of a total area of said surface; and ii) a second area of reflective patch; b) said diffuser further including a reflective well; c) said first area of absorbent patch, second area of reflective patch and reflective well combining together to form a variable impedance 2-dimensional array having pressure reflection coefficients of 0, 1 and-1, respectively. 42. The diffuser of claim 41, wherein said first area of absorbent patch and second area of reflective patch all have zero depth. 43. The diffuser of claim 42, wherein said reflective well has a depth comprising one-quarter of a wavelength at a design frequency of said diffuser. 44. The diffuser of claim 43, wherein said absorbent patch area, reflective patch area, and reflective well are arranged in a random or pseudo-random sequence, whereby sound scattered in a specular direction is suppressed by attenuation of the absorbent patch area and destructive interference between said reflective patch area and reflective well. 45. The diffuser of claim 44, wherein said absorbent patch area, reflective patch area, and reflective well are arranged in a ternary sequence, whereby sound scattered in a specular direction is suppressed by attenuation of the absorbent patch area and destructive interference between said reflective patch area and reflective well, more effectively than would be the case were the patch areas and well arranged in a random or pseudo-random sequence. 46. The diffuser of claim 41, wherein said reflective well comprises a plurality of wells, each having a depth of a quarter wavelength at a design frequency of said diffuser. 47. The diffuser of claim 41, wherein said absorptive and reflective patch areas and reflective wells, each have a shape chosen from the group consisting of square, rectangular, circular and triangular. 48. The diffuser of claim 41, wherein the absorbent area, reflective area and reflective well are arranged in a 2-dimensional array, using folding techniques that convert 1-dimensional ternary sequences into 2-dimensional sequences. 49. The diffuser of claim 41, wherein the absorbent area, reflective area and reflective well are arranged in a 2-dimensional array, using binary and ternary modulation and periodic multiplication of ternary sequences. 50. The diffuser of claim 41 formed into a 21��24 array, further including means for scattering sound in a hemisphere, by array manipulation of a ternary 21��6 sequence derived from periodic multiplication of two appropriate MLS sequences. 51. The diffuser of claim 50 formed by forming holes of any cross-section into a hard surface layer formed from wood, plastic or medium density fiberboard (MDF), with clear through holes accessing an absorbent backing forming R=0 wells, quarter wavelength deep reflective holes forming R=-1 wells, and flat reflective areas forming R=1 wells. 52. The diffuser of claim 51, in which the quarter wavelength deep holes consist of two different depths, with R=0, R=1, R=-1 and R=ξ pressure reflection coefficients arranged according to a quaternary sequence, where ξ is a coefficient generated by a rigid-walled well of a certain depth with /ξ/=1. 53. The diffuser of claim 51, formed by drilling R=-1 wells at different depths according to an optimal number theory sequence. 54. The diffuser of claim 50 formed using a thin template covering an absorbing panel, with clear through holes of any cross-section drilled at R=0 and R=-2 locations, with quarter wave deep reflective inserts placed into R=-1 hole locations and R=1 reflective areas simply left as is. 55. In a two-dimensional binary amplitude diffuser including a flat uniform thickness panel and a forward facing surface, said forward facing surface including sound reflective areas and sound absorptive areas formed by holes through said panel, the improvement comprising a recess formed in a rear surface of said panel, said recess encompassing a plurality of said holes, and an acoustical insert received within said recess. 56. The diffuser of claim 55, wherein said panel is generally rectangular. 57. The diffuser of claim 55, wherein said recess is generally circular. 58. The diffuser of claim 56, wherein said recess is generally circular. 59. The diffuser of claim 55, wherein said holes have circular cross-section. 60. The diffuser of claim 55, wherein said insert comprises a simple conical ramp. 61. The diffuser of claim 55, wherein said insert comprises an annular stepped ramp. 62. The diffuser of claim 55, wherein said insert comprises an annular stepped ramp with folded wells. 63. The diffuser of claim 55, wherein said insert comprises an annular phase grating. 64. The diffuser of claim 41 or 50, comprising a first diffuser and a second diffuser. 65. The diffuser of claim 64, wherein said first diffuser has absorptive and reflective patch areas and wells arranged in a first ternary sequence and said second diffuser has absorptive and reflective patch areas and wells arranged in a second ternary sequence. 66. The diffuser of claim 65, wherein said second ternary sequence is inverted with respect to said first ternary sequence. 67. The diffuser of claim 65, comprising a relatively large modulated diffuser consisting of said first and second diffuser arranged according to an optimal binary sequence in which a zero of said sequence refers to said first ternary sequence and a 1 of said sequence refers to said second ternary sequence, said second sequence being inverted with respect to said first sequence, thereby forming an aperiodic array using two base shapes. 68. The diffuser of claim 65, wherein said second ternary sequence is rotated with respect to the first ternary sequence. 69. The diffuser of claim 68, comprising a relatively large modulated diffuser consisting of said first and second diffuser arranged according to an optimal binary sequence in which a zero of said sequence refers to said first ternary sequence and a 1 of said sequence refers to said second rotated ternary sequence, thereby forming an aperiodic array using a single base shape.