APPARATUS FOR THE REDISTRIBUTION OF ACOUSTIC ENERGY

Abstract: An apparatus (1) for the redistribution of acoustic energy is provided which comprises a base (10), a lens (30), and a means for mounting a lens upon the base. The front surface of the lens includes a reflective surface. Acoustic energy output from a transducer (60) is redistributed by the apparatus (1).

Description: APPARATUS FOR THE REDISTRIBUTION OF ACOUSTIC ENERGY FIELD OF THE INVENTION This invention relates to reflective devices that, when coupled with a transducer, are capable of redistributing and broadly dispersing sound over a broad spectrum of frequencies with little or no distortion. BACKGROUND OF THE INVENTION It is well known in acoustics that the dispersion pattern of a sound source is related to the size of the radiating element. This causes conventional electro-acoustic transducers, or loudspeakers, to have an off-axis response that degrades with increasing frequency. This has long been regarded as a basic problem in loudspeaker design and over the years several different solutions have been proposed. These include the use of multiple transducers, horns and waveguides, electrostatic elements, and acoustic reflectors of varying shapes. Many of these solutions have undesirable side effects such as the introduction of frequency response anomalies and complicated fabrication techniques. Furthermore, these systems as well as conventional loudspeakers can act in 2 unpredictable ways in typical listening environments due to the lack of consideration usually given to the human auditory perceptual system. The recreation of sound via loudspeakers can be enhanced by controlling the direction, amplitude and spectral content of the sound arriving at the listener's ears via the loudspeaker/listening environment combination. It is the purpose of this invention to address all these issues in a single device which is simple to manufacture. When properly mated to a suitable conventional transducer, the invention causes sound to be transferred to the listening environment with a nearly frequency- invariant horizontal dispersion pattern. This affords a greater number of listeners with timbrally accurate sound with a greater sense of envelopment due to greatly enhanced lateral room reflections. Furthermore, floor and ceiling reflections are reduced causing increased stereophonic phantom image stability. A number of the invention's features can be modified to suit the designer's particular needs when incorporating the invention into a complete loudspeaker system. SUMMARY OF THE INVENTION The present invention addresses these concerns by providing an apparatus for the redistribution of acoustic power which comprises a base, a lens, and a means for mounting the lens upon the base. The base has an upper surface, a lower surface, a front surface, and a rear surface. The rear surface of the base is positionable upon a supporting surface. The lens also has an upper surface, a lower surface, a front surface, and a rear surface. The front surface of the lens includes a reflective surface, a point P lying on the reflective surface, and at least one adjoining surface SI. A line L passes through the point P and intersects the lower surface of the base at a point B. A point FI lies on the line L between the point P and the point B. The reflective surface is defined by the surface of revolution Rl of an elliptical arc Al rotated about the line L through an angle αl and the surface of revolution R2 of an elliptical arc A2 rotated about the line L through an angle α2. The elliptical arc Al constitutes a portion of an ellipse El having a focal point located at the point FI and having a lower end terminating at the point P. The elliptical arc A2 constitutes a portion of an ellipse E2 having a focal point located at said point FI and having an upper end 4 terminating at said point P. The angle αl is chosen such that the surface of revolution Rl is convex with respect to adjoining surface SI, and the angle α2 is chosen such that the surface of revolution R2 is concave with respect to adjoining surface SI. A primary object of the present invention is to provide an apparatus which redirects acoustic energy radiated from a sound radiator positioned at or proximate to focal point FI such that the resulting dispersion pattern is very broad over a very wide frequency range horizontally and is limited vertically. A further object of the present invention is to provide an apparatus which produces horizontally redirected acoustic radiation which is substantially free of frequency response anomalies. Another object of the present invention is to provide an apparatus with insulative surfaces positioned to tailor the overall acoustic radiation pattern. Other objects and advantages of the present invention will become apparent when the apparatus for redistribution of acoustic radiation of the present invention is considered in conjunction with the accompanying drawings, specification, and claims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side plan view of an embodiment of the inventive apparatus placed on a supporting surface showing the boundary of an interior reflective surface in phantom. Figure 2 is a front plan view of an embodiment of the inventive apparatus placed on a supporting surface. Figure 3 is a top plan view of an embodiment of the inventive apparatus showing the boundary of the exposed upper surface of its base member in phantom. Figure 4 is a cross-sectional view of the embodiment of the inventive apparatus of Figure 3 taken at section line 4-4 showing in phantom two ellipses used in the formation of the reflective surface of the inventive apparatus. Figure 5 is a diagram depicting the formation of the two surfaces of rotation which form the reflective surface of the inventive apparatus by the rotation of two elliptical arcs. Figure 6 is a side view of an embodiment of the inventive apparatus having a transducer mounted in a tilted orientation on the upper surface of its base. Figure 7 is a diagram showing the connection of a high pass filter between a power amplifier for the 6 sound system and a transducer used with the inventive apparatus. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figure 1, a preferred embodiment of the inventive apparatus 1 for redistribution of acoustic energy is shown. Apparatus 1 comprises a base 10, a lens 30, and a means for mounting lens 30 upon base 10. Base 10 has an upper surface 12 , a lower surface 14, a front surface 16, and a rear surface 18. Lower surface 14 is configured such that base 10 is positionable upon a supporting surface 20. Supporting surface 20 shown here is planar; it should be understood, however, that supporting surface 20 can be any surface upon which the user desires to place the inventive apparatus 1. Lens 30 has an upper surface 32, a lower surface 34, a front surface 36, and a rear surface 38. Referring to Figure 2, front surface 36 includes, but is not limited to, a reflective surface 50, a point P lying on reflective surface 50, and at least one adjoining surface SI. Additional adjoining surfaces such as S2 may also be designed. Reflective surface 50 is configured to provide optimal dispersion of acoustic radiation emitted from a transducer, and is defined by two surfaces of revolution Rl and R2. Referring to Figure 4, a line 7 L passes through the point P lying on reflective surface 50 and intersects the lower surface 14 of base 10 at a point B. Two ellipses El and E2 can then be chosen such that point P is located on each ellipse El and E2 , and ellipses El and E2 share a common focal point FI which lies on line L between point P and point B. Ellipse El then will have a second focal point F2,, and ellipse E2 will have a second focal point F2 2 . Ellipse El defines an elliptical arc Al having a lower end terminating at point P, and ellipse E2 defines an elliptical arc A2 having an upper end terminating at point P. Referring to Figure 5, surface of revolution Rl is formed by rotating elliptical arc Al through an angle l, and surface of revolution R2 is formed by rotating elliptical arc A2 through an angle α2. Angle αl should be chosen such that surface of revolution Rl is convex with regard to adjoining surface SI; angle oc2 should be chosen such that surface of revolution R2 is concave with regard to adjoining surface SI. In an embodiment of the inventive apparatus, the length of elliptical arc Al is varied constantly as it is rotated about line L at angles αl, while arc Al always terminates at lower point P. Effectively, this allows the user to produce a number of variances upon reflective surface Rl, each having a different upper boundary. 8 Referring to Figure 6, in operation, a transducer 60 is positioned at or proximate to point FI. Acoustic radiation is emitted from FI and disperses outward in all directions from the transducer's emissive area. Acoustic radiation dispersing towards lens 30 is reflected by reflective surface 50. While ellipses El and E2 may be any two ellipses selected to have the appropriate focal point FI, point P, and arc Al or A2 described above, they are preferably chosen such that most acoustic radiation striking surfaces Rl and R2 will be reflected upon paths which have a limited vertical component and a broad horizontal component. It should be understood, however, that the directivity of the reflected acoustic radiation, will depend upon many factors including, but not limited to, the positioning of the sound radiator producing the reflected acoustic radiation and the orientation of the reflective surface 50 with regard to the surrounding environment. The choice of ellipses El and E2 and the exact positioning of transducer 60 can be tailored to produce optimal effects. Transducer 60 may be tilted as shown in Figure 6, thus changing the direction at which the acoustic energy emitted from the transducer is radiated. The degree to which transducer 60 is tilted, which can be measured by an angle β made between an axis 62 of the 9 transducer 60 and the line L, can be varied to tailor the overall frequency response and vertical directivity of the apparatus. Referring to Figure 4, the surfaces of apparatus 1 other than reflective surface 50 also affect the overall sound production. Means for mounting lens 30 upon base 10 preferably comprises an absorptive material insulator 40 having an upper surface 42, a lower surface 44, a front surface 46, and a rear surface 48. Lower surface 44 of insulator 40 is fixed upon upper surface 12 of base 10. Lower surface 34 of lens 30 is fixed upon upper surface 42 of insulator 40. Insulator 40 may be composed of felt or any other appropriate absorptive material. Note that the vertical thickness of insulator 40 has been made large in Figures 1 and 4 for purposes of clarity of illustration. Benefits of the use of insulator 40 include, but are not limited to, the reduction of acoustic resonances that might otherwise degrade performance. The placement of insulator 40 may define a first covered portion 17 and a second uncovered portion 19 of the upper surface 12 of base 10. The uncovered portion 19 of upper surface 12 may slope downwardly. Benefits of such downward sloping include, but are not limited to, the tailoring of vertical dispersion to 10 suit the needs of the designer. It should be understood that absorptive material insulator could entirely cover upper surface 12 of base 10, if increased sound absorption is desired. Similarly, adjoining surfaces SI and 82 may be covered with some absorptive material 72 to absorb acoustic radiation which would otherwise reflect from them. This technique can be used to tailor overall system frequency response and limit the amount of horizontal dispersion. Considering the exterior surfaces of apparatus 1, curved surfaces will typically produce fewer disruptive diffraction effects. Accordingly, front surface 16 preferably forms a curvilinear arc, such as a generally elliptical or circular arc. Additionally, the rear surfaces 18, 38, and 48 of the base 10, lens 30, and insulator 40 preferably together form a rear surface 70 which is curvilinear and connects lower surface 14 of the base 10 to upper surface 32 of the lens 30. Preferably at least a portion of lower surface 14 is curvilinear and slopes upwardly to meet rear surface 70. Lower surface 14 and front surface 16 of base 10, rear surface 70, and upper surface 32 of lens 30 may also be covered with absorptive material 72 to inhibit diffraction effects. All conventional transducers have a sound power output that increases with decreasing frequency. 11 Since the apparatus equally redistributes sound power, the overall response of the system will have a corresponding rising response with decreasing frequency. Referring to Figure 7, to address this problem, in a preferred embodiment a simple high pass filter 100 which decreases electrical energy with decreasing frequency is connected to the transducer 60 of the inventive apparatus. The output of a signal source 110 used to drive the sound system passes through filter 100, causing the system to have an output at all frequencies that is substantially equal . Where multiple transducers 60 are installed in a sound system employing the apparatus, the filter may be part of the crossover network used to connect the multiple transducers 60. While the inventive apparatus has been described in terms of redistributing acoustic energy, it should be understood that the inventive apparatus could also be used to redistribute other energy waveforms such as electromagnetic waves. Although the foregoing invention has been described in some detail by way of illustration for purposes of clarity of understanding, it will be readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes and modifications may be made thereto 12 without departing from the spirit or scope of the appended claims.

Claims: 13 IT IS CLAIMED: 1. An apparatus 1 for the redistribution of acoustic energy, comprising: a base 10 having an upper surface 12 , a lower surface 14, a front surface 16, and a rear surface 18, said lower surface 14 positionable upon a supporting surface 20; a lens 30 having an upper surface 32, a lower surface 34, a front surface 36, and a rear surface 38; and means for mounting said lens 30 upon said base 10; said front surface 36 of said lens 30 including a reflective surface 50, a point P lying on said reflective surface 50, and at least one adjoining surface SI, a line L passing through said point P and intersecting the lower surface 14 of said base 10 at a point B, a point FI lying on said line L between said point P and said point B, said reflective surface 50 defined by the surface of revolution Rl of an elliptical arc Al rotated about said line L through an angle αl and the surface of revolution R2 of an elliptical arc A2 rotated about said line L through an angle α2 , said elliptical arc Al having a lower end terminating at said point P and constituting a portion of an ellipse El having a focal point located at said 14 point FI, said elliptical arc A2 having an upper end terminating at said point P and constituting a portion of an ellipse E2 having a focal point located at said point FI, said angle αl chosen such that said surface of revolution Rl is convex with respect to said adjoining surface SI, said angle α2 chosen such that said surface of revolution R2 is concave with respect to said adjoining surface SI. 2. The apparatus 1 of claim 1 wherein: said means for mounting said lens 30 upon said base 10 comprises an absorptive material insulator 40 having an upper surface 42, a lower surface 44, a front surface 46, and a rear surface 48; said absorptive material insulator 40 is fixed atop said upper surface 12 of said base 10 ; and said lens 30 is fixed atop said upper surface 42 of said absorptive material insulator 40. 3. The apparatus 1 of claim 2 further comprising a transducer 60 positioned at said point FI. 4. The apparatus 1 of claim 2 further comprising a transducer 60 positioned proximate to said point FI. 15 5. The apparatus 1 of claim 4 wherein said transducer 60 defines a central axis 62 and wherein said transducer 60 is tilted such that said central axis 62 of said transducer 60 intersects said line of rotation L at an acute angle β . 6. The apparatus 1 of claim 5 wherein said point FI lies proximate to said upper surface 12 of said base 10 and wherein said transducer 60 is mounted upon said upper surface 12 of said base 10. 7. The apparatus 1 of claim 6 wherein: said lower surface 44 of said absorptive material insulator 40 has a smaller surface area than does said upper surface 12 of said base 10 ; said absorptive material insulator 40 is positioned on said upper surface 12 to form a first covered portion 17 and a second uncovered portion 19 of said upper surface 12 ; and said second uncovered portion 19 slopes downwardly from said first covered portion 17. 8. The apparatus 1 of claim 7 wherein said front surface 16 of said base 10 is curvilinear. 16 9. The apparatus 1 of claim 8 wherein said front surface 16 of said base 10 is generally circular. 10. The apparatus 1 of claim 8 wherein said front surface 16 of said base 10 is generally elliptical. 11. The apparatus 1 of claim 8 wherein: said rear surfaces 18, 38, and 48 of said base 10, said lens 30, and said absorptive material insulator 40, respectively, together form a rear surface 70 for said apparatus 1 which is distal of said reflective surface 50 and connects said lower surface 14 of said base 10 to said upper surface 32 of said lens 30; and said rear surface 70 of said apparatus 1, said upper surface 32 of said lens 30, and at least a portion of said lower surface 14 of said base 10 are curvilinear. 12. The apparatus 1 of claim 11 wherein said elliptical arc Al has a constantly varying length as said elliptical arc Al is rotated about said line L. 17 13. The apparatus 1 of claim 12 wherein each said adjoining surface SI is covered with an absorptive material. 14. The apparatus 1 of claim 13 wherein said lower surface 14 and said front surface 16 of said base 10, said rear surface 70, and said upper surface 32 of said lens 30 are covered with an absorptive material . 15. The apparatus 1 of claim 14 wherein said transducer 60 produces an output, and further comprising a filter connected to said transducer 60, said filter modifying said output of said transducer such that said output has approximately equal energy at all frequencies.

Inventors: LACARRUBBA EMANUEL, LACARRUBBA, EMANUEL
Applicants: LACARRUBBA EMANUEL, LACARRUBBA, EMANUEL
Application year: 1999
Main classification: H05K5
IPC codes: G01S7, G10K11, G10K15, H04R1