Acoustic waveguiding

• US 20050205348A1
• Filed: 03/19/2004
• Published: 09/22/2005
• Est. Priority Date: 03/19/2004
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Parker, Robert Preston, Greenberger, Hal P., Potter, Dewey
• Granted Patent: US 7,565,948 B2
• Time in Patent Office: Days
• US Class Current: 181/155
• CPC Class Codes: H04R 1/2857 for loudspeaker transducers
• CPC Class Codes: H04R 2205/022 Plurality of transducers corresponding to a plurality of sound channels in each earpiece of headphones or in a single enclosure
• CPC Class Codes: H04R 5/02 Spatial or constructional arrangements of loudspeakers

Abstract

An acoustic waveguide system contains a trunk waveguide and a number of branch waveguides. The trunk waveguide section defines an interior passage and includes at least one open end. A number of branch waveguide sections define an interior passage and include a junction end and a terminal end, with the junction end coupled to the trunk waveguide. One or more cavities can be coupled to at least one of the trunk or branch sections and communicate therewith through a vent for damping the resonance peak of a target standing wave.

Claims

1. An apparatus comprising

a trunk acoustic waveguide section having a free end, and

branch acoustic waveguide sections each having a junction end coupled to the trunk and a terminal end to receive an acoustic energy source.

2. The apparatus of claim 1 in which the cross-sectional area of at least one of the branch sections decreases from the terminal end to the junction end.

3. The apparatus of claim 1 in which internal volumes of the branch waveguides are substantially the same.

4. The apparatus of claim 1 also including the acoustic energy source.

5. The apparatus of claim 4 in which the acoustic energy source includes an acoustic driver.

6. The apparatus of claim 5 wherein the acoustic driver includes a first radiating surface acoustically coupled to the terminal end of the branch section and a second radiating surface facing free air.

7. The apparatus of claim 6 wherein the second radiating surfaces are oriented toward a listening area.

8. The apparatus of claim 1 also including a main housing and in which the branch waveguide sections further comprise subsections, the subsections partially formed by panels extending from inside surfaces of the main housing.

9. The apparatus of claim 1 in which the lengths of the subsections of respective branch sections are substantially the same.

10. The apparatus of claim 1 in which the cross-sectional area of the trunk waveguide section increases along the length from the free end.

11. The apparatus of claim 1 in which at least two of the branch waveguide sections are coupled at different locations along the trunk section.

12. The apparatus of claim 1 in which the terminal end of the branch waveguide sections are spatially separated.

13. The apparatus of claim 8 wherein the main housing is substantially trapezoidal.

14. The apparatus of claim 1 in which the branch waveguide sections have unequal lengths.

15. An acoustic waveguide system comprising

a trunk waveguide section having a single free end;

first and second branch waveguide sections coupled to the trunk waveguide section at locations other than the free end; and

each of the first and second waveguide sections having a terminal end acoustically coupled to an acoustic energy source including at least one acoustic driver.

16. The acoustic waveguide system in claim 15 in which the first and second waveguide sections have substantially the same length.

17. The acoustic waveguide system in claim 15 in which the first and second waveguide sections have substantially the same cross-sectional area along their lengths.

18. The acoustic waveguide system in claim 15 in which the terminal ends of the first and second waveguide sections are spatially separated from each other.

19. The acoustic waveguide system in claim 15 in which a cross-sectional area of the trunk waveguide section progressively increases along the length from the free end.

20. The acoustic waveguide system in claim 15 in which the acoustic driver comprises a first radiating surface facing free air and a second radiating surface, opposite the first surface, acoustically coupled to the branch waveguide section.

21. The acoustic waveguide system in claim 20 in which the first radiating surface faces a listening area.

22. The acoustic waveguide system in claim 21 further includes an electronic device which uses acoustic energy sources to provide program information to the first and second waveguide sections.

23. An audio player comprising

a housing,

an electronic audio circuit,

an acoustic energy source coupled to the electronic audio circuit, and

a waveguide structure comprising

a trunk acoustic waveguide section having a free end, and

a plurality of branch acoustic waveguide sections each having a junction end coupled to the trunk and a terminal end to receive an acoustic energy source.

24. An electroacoustical waveguide transducing system comprising

a trunk acoustic waveguide section having a free end,

first and second branch acoustic waveguide sections each having a junction end coupled to the trunk and a terminal end to receive an acoustic energy source, and

an elongate cavity defining a volume substantially smaller than the volume of the trunk and branch sections, the cavity linked to at least one of the branch sections and trunk section by an aperture, and

first and second acoustic energy sources coupled to the terminal ends of the first and second branch waveguide sections and comprising

first and second acoustic drivers each comprising a first radiating surface acoustically coupled to the terminal ends of the first and second sections and a second radiating surface facing the free air.

25. The system of claim 24 in which the relationship between the cross-sectional area of the free end, A and the wavelength of sound at a low frequency cutoff of the waveguide, λ

is given by;

({square root}{square root over (A)})/λ

≦

0.067.

26. The system of claim 25 in which the low frequency cutoff is about 55 Hz.

27. The system of claim 25 in which the cross-sectional area, A is about 2.5 sq. in.

28. An apparatus comprising

an acoustic waveguide system having a tree-structure and comprising:

a first number of open end root nodes,

a second number of terminal end leaf nodes, and

the first number of open end root nodes being connected to the second number of terminal end leaf nodes via a plurality of internal waveguide sections and a third number of internal nodes,

wherein each one of the second number of terminal leaf nodes is acoustically coupled to an acoustic energy source.

29. The apparatus of claim 28 wherein the second number is larger than the first number.

30. The apparatus of claim 28 in which the first number of open end root nodes are spatially separated from each other.

31. The apparatus of claim 28 in which each of the second number of terminal end leaf nodes are coupled to an acoustic energy source.

32. The apparatus of claim 31 wherein the acoustic energy source comprises at least one acoustic driver.

33. The apparatus of claim 28 in which the second number of terminal end leaf nodes are spatially separated from each other.

34. The apparatus of claim 28 in which different program information is fed into the second number of terminal end leaf nodes.

35. An apparatus comprising

a trunk acoustic waveguide section having a free end,

first and second branch acoustic waveguide sections each having a junction end coupled to the trunk and a terminal end to receive an acoustic energy source, and

an elongate cavity defining a volume substantially smaller than the volume of the trunk and branch sections, the cavity attaching to at least one of the branch sections and trunk section via a vent which forms an aperture between the sections and the cavity,

wherein the elongate cavity is sized and the vent is positioned along at least one of the branch and trunk sections to substantially reduce a resonance peak.

36. The apparatus of claim 35 in which the elongate cavity comprises a bifurcated resonance chamber.

37. The apparatus of claim 35 further comprising acoustic dampening material positioned within the elongate cavity.

38. An electroacoustical waveguide transducing system comprising

a waveguide having a free end and closed end, and

an elongate cavity defining a volume substantially smaller than the volume of the waveguide, the cavity attaching to the waveguide via a vent, the vent located at a point along the length of the waveguide corresponding or close to the pressure maximum of a target standing wave within the waveguide.

39. The electroacoustical waveguide transducing system of claim 38 in which the length of the elongate cavity is about one quarter of the wavelength of the target standing wave.

40. The system of claim 38 further comprising

first and second branch acoustic waveguide sections each having a junction end coupled to the closed end and a terminal end to receive an acoustic energy source, and

first and second acoustic drivers each comprising a first radiating surface acoustically coupled to the terminal ends of the first and second sections and a second radiating surface facing the free air.

41. The system of claim 40 in which the relationship between the cross-sectional area of the free end, A and the wavelength of sound at a low frequency cutoff of the waveguide, λ

is given by;

({square root}{square root over (A)})/λ

≦

0.067.

42. The system of claim 38 further comprising acoustic dampening material positioned proximate the vent.

43. The system of claim 38 further comprising acoustic dampening material positioned within the elongate cavity.