Noise canceling microphone system and method for designing the same
First Claim
1. An active noise canceling microphone system comprising:
- a first microphone element comprising a first back surface and a first sound pressure sensitive surface for receiving a first microphone signal comprising speech and noise and a second microphone element comprising a second back surface and a second sound pressure sensitive surface for receiving a second microphone signal containing primarily noise, wherein the first and second microphone elements have a diameter “
d” and
a thickness “
t”
; and
a hollow cylindrically shaped microphone housing having an outside diameter “
D,”
an interior cavity of diameter of “
d,” and
a height “
2t”
, wherein the microphone housing is adapted to secure the first and second microphone elements aligned axially with the back surfaces in contact, and wherein the ratio of “
D”
over “
d”
is between 1 and about 2.4.
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Accused Products
Abstract
A microphone housing improves the broadband noise canceling performance of an active noise canceling microphone system while also ensuring improved speech transmission through the system. First and second microphone elements are selected each having a diameter “d” and a thickness “t”. The two microphone elements are aligned axially with the back surfaces in contact and secured in an axially aligned cylindrical cavity within a cylindrically shaped housing. The cylindrically shaped housing has an outside diameter “D,” an interior cavity of diameter of “d,” and a height “2t”. The housing is exposed to an environment comprising both speech and noise. The first microphone element is adapted to receive a signal having both voice and noise components, while the second microphone element is adapted to receive a signal that is predominantly noise. A controller processes signals from the first microphone element and the second microphone element. The values of D and d are selected so to obtain a ratio of D over d between 1 and about 2.4 or a near field power difference of the first microphone signal and the second microphone signal between 8 dB and 11 dB. In the event the near field power difference is more than 11 dB, the outside diameter of the microphone housing “D” is reduced. In the event the near field power difference is less than 8 dB, the outside diameter of the microphone housing “D” is increased.
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Citations
54 Claims
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1. An active noise canceling microphone system comprising:
-
a first microphone element comprising a first back surface and a first sound pressure sensitive surface for receiving a first microphone signal comprising speech and noise and a second microphone element comprising a second back surface and a second sound pressure sensitive surface for receiving a second microphone signal containing primarily noise, wherein the first and second microphone elements have a diameter “
d” and
a thickness “
t”
; and
a hollow cylindrically shaped microphone housing having an outside diameter “
D,”
an interior cavity of diameter of “
d,” and
a height “
2t”
, wherein the microphone housing is adapted to secure the first and second microphone elements aligned axially with the back surfaces in contact, and wherein the ratio of “
D”
over “
d”
is between 1 and about 2.4. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An active noise canceling microphone system comprising:
-
a first microphone element comprising a first back surface and a first sound pressure sensitive surface for receiving a first microphone signal comprising speech and noise and a second microphone element comprising a second back surface and a second sound pressure sensitive surface for receiving a second microphone signal containing primarily noise, wherein both the first and second microphone elements have a diameter “
d” and
a thickness “
t”
; and
a hollow cylindrically shaped microphone housing comprising an outside diameter “
D,”
an interior cavity of diameter of “
d,” and
a height “
2t”
, wherein the microphone housing is adapted to secure the first and second microphone elements aligned axially with the back surfaces in contact, and wherein the ratio of “
D”
over “
d”
is selected to obtain a near field power difference between the first microphone signal and the second microphone signal in an acoustic environment comprising both speech and noise in the range of 8 dB to 11 dB. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. An active noise canceling microphone system comprising:
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a first microphone element comprising a first back surface and a first sound pressure sensitive surface for receiving a first microphone signal comprising speech and noise and a second microphone element comprising a second back surface and a second sound pressure sensitive surface for receiving a second microphone signal containing primarily noise, wherein both the first and second microphone elements have a diameter “
d” and
a thickness “
t”
; and
a microphone housing symmetrical about a vertical axis comprising a height “
2t,”
a bottom of outside diameter D1 and a top of outside diameter D2, wherein D1>
D2, and an internal cylindrical cavity axially aligned with the top and bottom and comprising a diameter of “
d,”
wherein the microphone housing is adapted to secure the first microphone element in the top portion of the microphone housing and the second microphone element in the bottom portion of the microphone housing so that the first and second microphone elements are aligned axially with their back surfaces in contact, and wherein the ratio of “
D2”
to “
d”
is between 1 and about 2.4 - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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28. An active noise canceling microphone system comprising:
-
a first microphone element comprising a first back surface and a first sound pressure sensitive surface for receiving a first microphone signal comprising speech and noise and a second microphone element comprising a second back surface and a second sound pressure sensitive surface for receiving a second microphone signal containing primarily noise, wherein both the first and second microphone elements have a diameter “
d” and
a thickness “
t”
; and
a microphone housing symmetrical about a vertical axis having a height “
2t,”
a bottom of outside diameter D1 and a top of outside diameter D2, wherein D1>
D2, and an internal cylindrical cavity axially aligned with the top and bottom and having a diameter of “
d,”
wherein the microphone housing is adapted to secure the first microphone element in the top portion of the microphone housing and the second microphone element in the bottom portion of the microphone housing so that the first and second microphone elements are aligned axially with their back surfaces in contact, and wherein the ratio of “
D2”
to “
d”
is selected to obtain a near field power difference between the first microphone signal and the second microphone signal in an acoustic environment comprising both speech and noise in the range of 8 dB to 11 dB. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36)
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37. An active noise canceling microphone system comprising:
-
a first microphone element comprising a first back surface and a first sound pressure sensitive surface for receiving a first microphone signal comprising speech and noise and a second microphone element comprising a second back surface and a second sound pressure sensitive surface for receiving a second microphone signal containing primarily noise, wherein both the first and second microphone elements have a diameter “
d” and
a thickness “
t”
;
a first cap covering the first microphone element, wherein the first cap comprises at least one opening, and a second cap covering the second microphone element, wherein the second cap comprises at least one opening, and wherein the thickness of the first and second cap is no greater than required to protect the first and second sound pressure sensitive surfaces; and
an external concave curved-shaped microphone housing symmetrical about a vertical axis having a height “
2t,”
a bottom of outside diameter D1 and a top of outside diameter D2, wherein D1>
D2, and an internal cylindrical cavity axially aligned with the top and bottom and having a diameter of “
d,”
wherein the microphone housing is adapted to secure the first microphone element in the top portion of the microphone housing and the second microphone element in the bottom portion of the microphone housing so that the first and second microphone elements are aligned axially with their back surfaces in contact, and wherein the ratio of “
D2”
to “
d”
is between 1 and about 2.4 - View Dependent Claims (38, 39, 40, 41, 42, 43, 44, 45)
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46. An active noise canceling microphone system comprising:
a first microphone element comprising a first back surface and a first sound pressure sensitive surface for receiving a first microphone signal comprising speech and noise and a second microphone element comprising a second back surface and a second sound pressure sensitive surface for receiving a second microphone signal containing primarily noise, wherein both the first and second microphone elements have a diameter “
d” and
a thickness “
t”
; and
an external concave curved-shaped microphone housing symmetrical about a vertical axis having a height “
2t,”
a bottom of outside diameter D1 and a top of outside diameter D2, wherein D1>
D2, and an internal cylindrical cavity axially aligned with the top and bottom and having a diameter of “
d,”
wherein the microphone housing is adapted to secure the first microphone element in the top portion of the microphone housing and the second microphone element in the bottom portion of the microphone housing so that the first and second microphone elements are aligned axially with their back surfaces in contact, and wherein the ratio of “
D2”
to “
d”
is selected to obtain a near field power difference between the first microphone signal and the second microphone signal in an acoustic environment comprising both speech and noise in the range of 8 dB to 11 dB.- View Dependent Claims (47, 48, 49, 50, 51, 52, 53, 54)
Specification