Electroacoustic waveguide transducing

• US 20020085731A1
• Filed: 01/02/2001
• Published: 07/04/2002
• Est. Priority Date: 01/02/2001
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Aylward, J. Richard
• Granted Patent: US 7,426,280 B2
• Time in Patent Office: Days
• US Class Current: 381/349
• CPC Class Codes: H04R 1/227 using transducers reproducing the same frequency band
• CPC Class Codes: H04R 1/2857 for loudspeaker transducers

Abstract

An acoustic waveguide system, having source of acoustic radiation and a source of opposing acoustic radiation. An acoustic waveguide has an open end and an interior. A first acoustic driver having a first radiating surface and a second radiating surface is arranged and constructed so that the first radiating surface radiates sound waves into free air and the second radiating surface radiates sound waves into the acoustic waveguide so that sound waves are radiated at the open end. A source of opposing sound waves in the acoustic waveguide opposes a predetermined spectral component of the sound waves radiated into the acoustic waveguide to reduce the acoustic radiation of the predetermined spectral component from the acoustic waveguide.

Claims

1. An electroacoustic waveguide system, comprising:

an acoustic waveguide having an open end and an interior;

a first acoustic driver having a first radiating surface and a second radiating surface, constructed and arranged so that said first radiating surface radiates sound waves into free air and said second radiating surface radiates sound waves into said acoustic waveguide so that sound waves are radiated at said open end; and

a source of opposing sound waves in said acoustic waveguide for opposing a predetermined spectral component of said sound waves radiated into said acoustic waveguide to oppose the acoustic radiation of said predetermined spectral component from said acoustic waveguide.

2. An electroacoustic waveguide system in accordance with claim 1, further comprising an acoustic port, coupling said interior with free air.

3. An electro acoustic waveguide system in accordance with claim 1, wherein said predetermined spectral component comprises the opposition frequency.

4. An electroacoustic waveguide system in accordance with claim 1, wherein said source of opposing sound waves comprises a reflective surface inside said acoustic waveguide, positioned so that sound waves reflected from said reflective surface oppose said sound waves radiated directly into said acoustic waveguide by said second radiating surface.

5. An electroacoustic waveguide system in accordance with claim 1, wherein said source of opposing sound waves comprises a second acoustic driver arranged and constructed to radiate sound waves into said acoustic waveguide.

6. An electroacoustic waveguide system in accordance with claim 5, further comprising an acoustic port, coupling said interior with free air.

7. An electroacoustic waveguide system in accordance with claim 6, wherein said acoustic waveguide has a closed end and said acoustic port is positioned between said first acoustic driver and said closed end of said acoustic waveguide.

8. An electroacoustic waveguide system in accordance with claim 1, wherein said predetermined spectral component comprises a dip frequency at which said waveguide system produces an acoustic null, absent said source of opposing sound waves.

9. An electroacoustic waveguide system in accordance with claim 8, wherein said source of opposing sound waves comprises a reflective surface inside said acoustic waveguide, positioned so that sound waves reflected from said reflective surface opposes said sound waves radiated directly into said acoustic waveguide by said second radiating surface.

10. An electroacoustic waveguide system in accordance with claim 8, wherein said source of opposing sound waves comprises a second acoustic driver arranged and constructed to radiate sound waves into said acoustic waveguide.

11. An electroacoustic waveguide system, comprising:

an acoustic waveguide having an open end and a closed end and further having an effective length;

an acoustic driver for radiating sound waves into said waveguide, positioned in said acoustic waveguide so that there is an acoustic null at said open end at a dip frequency.

12. An electroacoustic waveguide system in accordance with claim 11, said acoustic waveguide having a substantially constant cross section, wherein said acoustic driver is positioned at a distance substantially 0.25L from said closed end of said waveguide, where L is the effective length of said waveguide.

13. An electroacoustic waveguide system in accordance with claim 12, wherein said closed end is a surface that is acoustically reflective at said dip frequency.

15. An electroacoustic waveguide system in accordance with claim 14, wherein a second of said acoustic drivers is positioned in said closed end of said acoustic waveguide.

16. An electroacoustic waveguide system in accordance with claim 14, wherein a second of said plurality of acoustic drivers is placed in said wall of said acoustic waveguide so that said first radiating surface of said second driver radiates into said acoustic waveguide and said second radiating surface of said second acoustic driver radiates into free air.

17. A method for radiating with the apparatus of claim 14 by combining radiation of said plurality of acoustic drivers to produce an acoustic null at the open end of said waveguide at a dip frequency.

19. An electroacoustic waveguide system in accordance with claim 18, wherein said acoustic low pass-filter comprises an acoustic compliance between said acoustic driver and said acoustic waveguide.

14. An electroacoustic waveguide system comprising:

an acoustic waveguide having an open end and a closed end and a wall connecting said open end and said closed end;

a plurality of acoustic drivers, each having a first radiating surface and a second radiating surface;

wherein a first of said acoustic drivers is placed in said wall of said acoustic waveguide so that said first radiating surface of said first acoustic driver radiates into said acoustic waveguide and said second radiating surface of said first acoustic driver radiates into free air.

18. An electroacoustic waveguide system comprising:

an acoustic waveguide;

an acoustic driver; and

an acoustic low-pass filter intercoupling said acoustic driver and said acoustic waveguide.

20. An electroacoustic waveguide system comprising:

an acoustic waveguide having an open end and a closed end and an effective midpoint;

a plurality of acoustic drivers; and

an acoustic compliance acoustically coupling a first of said plurality of acoustic drivers and said acoustic waveguide.

21. An electroacoustic waveguide system in accordance with claim 20 wherein a first of said plurality of acoustic drivers is positioned at approximately said effective midpoint.

22. An electroacoustic waveguide system in accordance with claim 20,

said acoustic waveguide having a substantially constant cross section,

wherein a first of said plurality of acoustic drivers is positioned at a distance substantially 0.25L from said closed end, where L is the effective length of said acoustic waveguide,

and wherein a second of said plurality of acoustic drivers is positioned substantially 0.75L from said closed end,

and an acoustic compliance between said second acoustic driver and said waveguide.

24. An electroacoustic waveguide system in accordance with claim 23 wherein a first of said plurality of acoustic drivers is placed at a position substantially 0.25L from said closed end and a second of said acoustic drivers is placed at a position substantially 0.75L from said closed end, where L is the effective length of the waveguide.

26. A method for operating an acoustic waveguide in accordance with claim 25, wherein said opposing acoustic radiation comprises providing opposing acoustic radiation in said acoustic waveguide.

27. A method for operating an acoustic waveguide in accordance with claim 26, wherein said providing opposing acoustic radiation comprises reflecting said radiated acoustic energy off an acoustically reflective surface inside said acoustic waveguide so that said reflected acoustic energy opposes the acoustic energy radiated into said waveguide.

28. A method for operating an acoustic waveguide in accordance with claim 26, wherein said providing opposing acoustic radiation comprises radiating, by a second acoustic driver, said opposing acoustic energy into said acoustic waveguide.

23. An electroacoustic waveguide system comprising:

an acoustic waveguide having a substantially constant cross section; and

a plurality of acoustic drivers placed in said acoustic waveguide so at least two of said acoustic drivers are substantially 0.5L apart where L is the effective length of the waveguide.

25. A method for operating an acoustic waveguide having an open end and a closed end and a wall connecting said open end and said closed end, comprising,

radiating acoustic energy into said acoustic waveguide;

and

significantly opposing acoustic radiation at a predetermined dip frequency.