Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Having acoustic wave modifying structure
Patent
1996-06-10
1998-06-09
Kuntz, Curtis A.
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Having acoustic wave modifying structure
381188, 381169, 381205, 181155, 181156, 333193, 2961801, H04R 2500
Patent
active
057647828
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an acoustic reflector, and in particular, to an acoustic reflector that provides a broad angle within which maximal energy is reflected from a source.
BACKGROUND OF THE INVENTION
A conventional loudspeaker radiates acoustic energy directly into a listening environment. Such a direct radiating loudspeaker driver suffers from a high directivity factor. That is, it directs greater amounts of acoustic energy to locations at some angles from the loudspeaker driver than it does to locations at other angles. For optimal "listening", such a conventional loudspeaker requires careful aiming of the loudspeaker relative to the preferred listening point.
A prior art attempt at broadening the optimum listening angle is described in U.S. Pat. No. 4,800,983, issued on Jan. 31, 1989 ("the No. '983 patent"). The No. '983 patent describes acoustic wave "diffractor" labyrinth(s) positioned obliquely in front of sound producing transducer(s). This arrangement is described as causing wide angle dispersion of sound waves projected from the transducer(s) into the labyrinth(s).
A problem with the arrangement described in the No. '983 patent is that the labyrinth and the tweeter will both radiate energy in the solid half space from .pi./2 to -.pi./2. Since the radiating sound producing transducers are in oblique alignment to the labyrinth, the energy produced by the transducers will interfere with the radiated energy from the labyrinth. This will cause reflected energy to radiate off the sound producing transducers and cause interference to the resultant sound field, and it also reduces the angle of radiation below .pi. radians.
SUMMARY OF THE INVENTION
The present invention is an acoustic reflector for reflecting waves from a source. The reflector comprises a surface facing the source. The surface has a plurality (N) of wells, where N is an odd prime number, running along a length direction of the surface. Each well has a depth D.sub.n =(n.sup.2 rem N) * unit depth (0<=n<=N-1), governed by a Quadratic Residue Sequence. Thus, acoustic energy directed from the source to the reflector, and reflected from the reflector, has substantially equal acoustic energy in all angular directions from the reflector within plus and minus .pi./2 from the direction of radiation.
In a further embodiment in accordance with the present invention, the depth of each well is corrected by the variance between a spherical wave from the source and the distance from the surface of the reflector to the source.
In another embodiment of the invention, a reflector has a plurality of wells with each of the wells having depths D.sub.n =(n.sup.2 rem N) * unit depth, governed by a Quadratic Residue Sequence, and a radiating source coupled at an extremity of each of the wells.
In a still further embodiment of the invention, a reflector has a plurality of wells where the wells have depths governed by a Quadratic Residue Sequence, and a radiating source is positioned at the extremity of each well.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an acoustic source in relation to a reflector.
FIG. 2A is a cross-sectional view taken along 3--3 of FIG. 1 of a reflector in accordance with the present invention having wells in the surface, the depths of the wells governed by a Quadratic Residue Sequence.
FIG. 2B is a cross-sectional view of another embodiment of a reflector in accordance with the present invention having a series of nested wells, with each nest governed by a Quadratic Residue Sequence.
FIG. 3 is a cross-sectional view taken along 3--3 of FIG. 1, or one embodiment of an improved reflector in accordance with the present invention.
FIG. 4 is a perspective cutaway view of the embodiment of FIG. 1, where the well bottoms are concave.
FIG. 5 is a perspective cutaway view of the embodiment of FIG. 1, where the well bottoms are convex.
FIG. 6A is a plan view of an embodiment in accordance with the present invention wherein acoustic sources are placed within wells whose
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M.R. Schroeder and R.E. Gerlach "Diffuse Sound Reflection Surfaces", 9th ICA, Madrid, Paper D8 (1977) Sep. 3, 1977.
Barnie Rexford N.
Kuntz Curtis A.
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