Pipe calibration method for omnidirectional microphones
Embodiments include a method comprising forming a pipe including a first end and a second end by forming couplings between a plurality of sections of pipe. A loudspeaker is connected to the first end. The loudspeaker is a mouth simulator loudspeaker. A plurality of microphones are positioned a third distance inside an inside surface of the pipe using a receptacle positioned in the pipe a first distance from the first end and a second distance from the second end. An acoustic output is generated at the loudspeaker. One or more calibration filters are generated using outputs of the plurality of microphones produced in response to the acoustic output.
1. A method comprising:
forming a pipe including a hole in the pipe configured to receive a headset mount, a first end and a second end by forming couplings between a plurality of sections of pipe, each coupling comprises a union configured to join adjacent sections of the plurality of sections of pipe, the adjacent sections being positioned in an inside diameter of a respective union, and the adjacent sections in each union being spaced apart from each other by a gap;
connecting a loudspeaker to the first end, wherein the loudspeaker is a mouth simulator loudspeaker;
placing an electronic device having a plurality of microphones substantially within a receptacle of the headset mount;
holding the electronic device securely to the receptacle using a firm foam piece substantially disposed at an end of a toggle clamp;
positioning the headset mount in the hole in the pipe with each of the plurality of microphones substantially disposed a third distance inside an inside surface of the pipe, the receptacle being positioned in the pipe a first distance from the first end and a second distance from the second end;
generating an acoustic output at the loudspeaker; and
generating at least one calibration filter using outputs of the plurality of microphones produced in response to the acoustic output.
2. The method of claim 1 , comprising coupling the at least one calibration filter to the output of the plurality of microphones, wherein the at least one calibration filter includes coefficients that filter an output of each microphone so that an amplitude and phase of the plurality of microphones are approximately equal in response to an identical input.
3. The method of claim 1 , wherein the forming of the pipe comprising forming the pipe with a cylindrical cross-section.
4. The method of claim 1 , wherein forming couplings between a plurality of sections of pipe comprises forming couplings between the plurality of sections including five sections.
5. The method of claim 4 , wherein a first section comprises the first end, a second section is coupled to the first section and comprises the receptacle, and a fifth section comprises the second end.
6. The method of claim 5 , comprising a third section coupled to the second section, wherein the first section and the third section have an equivalent length.
7. The method of claim 6 , wherein a length of the first section and the third section is approximately 48 centimeters.
8. The method of claim 6 , wherein a length of the second section is approximately 17 centimeters.
9. The method of claim 6 , comprising a fourth section coupled to the third section, wherein the fifth section is coupled to the fourth section, wherein the fourth section and the fifth section have an equivalent length.
10. The method of claim 9 , wherein a length of the fourth section and the fifth section is approximately 28 centimeters.
11. The method of claim 9 , comprising positioning an absorbing material between the receptacle and the second end of the pipe.
12. The method of claim 11 , comprising positioning the absorbing material inside at least a portion of the pipe comprising the third section, the fourth section, and the fifth section.
13. The method of claim 12 , comprising wedging the absorbing material in the third section at an end nearest the receptacle.
14. The method of claim 4 , wherein the first distance is approximately 57 centimeters.
15. The method of claim 1 , wherein forming couplings between a plurality of sections of pipe comprises forming couplings between the plurality of sections including four sections.
16. The method of claim 15 , wherein a first section comprises the first end, and a second section is coupled to the first section and comprises the receptacle.
17. The method of claim 16 , wherein a length of the second section is approximately 17 centimeters.
18. The method of claim 16 , comprising a third section coupled to the second section.
19. The method of claim 18 , wherein a length of the third section is approximately 48 centimeters.
20. The method of claim 18 , comprising a fourth section coupled to the third section, wherein the first section and the fourth section have an equivalent length.
21. The method of claim 20 , wherein a length of the first section and the fourth section is approximately 28 centimeters.
22. The method of claim 15 , wherein the first distance is approximately 37 centimeters.
23. The method of claim 1 , wherein forming couplings between a plurality of sections of pipe comprises forming couplings between the plurality of sections including three sections.
24. The method of claim 23 , wherein a first section comprises the first end, and a second section is coupled to the first section and comprises the receptacle.
25. The method of claim 24 , wherein a length of the second section is approximately 17 centimeters.
26. The method of claim 24 , comprising a third section coupled to the second section, wherein the first section and the third section have an equivalent length.
27. The method of claim 26 , wherein a length of the first section and the third section is approximately 48 centimeters.
28. The method of claim 27 , wherein the first distance is approximately 57 centimeters.
29. The method of claim 26 , wherein a length of the first section and the third section is approximately 28 centimeters.
30. The method of claim 29 , wherein the first distance is approximately 37 centimeters.
31. The method of claim 24 , comprising a third section coupled to the second section, wherein the first section and the third section have different lengths.
32. The method of claim 31 , wherein a length of the first section is approximately 48 centimeters.
33. The method of claim 32 , wherein a length of the third section is approximately 28 centimeters.
34. The method of claim 33 , wherein a length of the second section is approximately 17 centimeters.
35. The method of claim 34 , wherein the first distance is approximately 57 centimeters.
36. The method of claim 32 , wherein a length of the first section is approximately 28 centimeters.
37. The method of claim 36 , wherein a length of the third section is approximately 48 centimeters.
38. The method of claim 37 , wherein a length of the second section is approximately 17 centimeters.
39. The method of claim 38 , wherein the first distance is approximately 37 centimeters.
40. The method of claim 31 , wherein a length of the first section is approximately 15 centimeters.
41. The method of claim 40 , wherein a length of the third section is approximately 28 centimeters.
42. The method of claim 41 , wherein a length of the second section is approximately 17 centimeters.
43. The method of claim 42 , wherein the first distance is approximately 24 centimeters.
44. The method of claim 23 , wherein a first section comprises the first end and the receptacle.
45. The method of claim 44 , comprising a second section coupled to the first section, and a third section coupled to the second section, wherein the third section comprises the second end.
46. The method of claim 45 , wherein a length of the first section is approximately 17 centimeters.
47. The method of claim 46 , wherein a length of the second section is approximately 48 centimeters.
48. The method of claim 47 , wherein a length of the third section is approximately 28 centimeters.
49. The method of claim 48 , wherein the first distance is approximately 8 centimeters.
50. The method of claim 1 , wherein the forming couplings between a plurality of sections comprises forming couplings between the plurality of sections including two sections.
51. The method of claim 50 , wherein a first section comprises the first end and the receptacle.
52. The method of claim 51 , comprising a second section coupled to the first section, wherein the second section comprises the second end.
53. The method of claim 52 , wherein a length of the first section is approximately 17 centimeters.
54. The method of claim 53 , wherein a length of the second section is approximately 48 centimeters.
55. The method of claim 54 , wherein the first distance is approximately 8 centimeters.
56. The method of claim 53 , wherein a length of the second section is approximately 28 centimeters.
57. The method of claim 56 , wherein the first distance is approximately 8 centimeters.
58. The method of claim 1 , wherein the first distance is at least 30 centimeters.
59. The method of claim 1 , wherein the second end is open.
60. The method of claim 1 , wherein the second end is coupled to a cap, wherein the cap closes the second end.
61. The method of claim 60 , wherein the cap is tapered.
62. The method of claim 61 , wherein an inside diameter of the cap changes linearly as a function of a length of the cap.
63. The method of claim 62 , wherein the length of the cap is in a approximately in a range of 2 inches to 34 inches.
64. The method of claim 1 , wherein an inside diameter of the pipe is approximately in a range of 2 inches to 4 inches.
65. The method of claim 1 , wherein the third distance is approximately in a range of 2 to 5 millimeters.
66. The method of claim 1 , wherein the headset mount locates each microphone of the plurality of microphones an equal distance from the loudspeaker.
67. The method of claim 1 , comprising an absorbing material positioned inside at least a portion of the pipe.
68. The method of claim 67 , wherein the absorbing material is positioned between the receptacle and the second end of the pipe.
69. The method of claim 68 , wherein the absorbing material is wedged at an end nearest the receptacle.
70. The method of claim 67 , wherein an amount of the absorbing material is an amount that lowers an amount of reflected acoustic energy returning to the plurality of microphones from the second end at least 40 decibels lower than acoustic energy projected from the first end.
71. The method of claim 67 , wherein the absorbing material comprises bonded absorbent cotton.
72. The method of claim 1 , wherein the plurality of sections is straight.
73. The method of claim 1 , wherein at least one section of the plurality of sections is curved.