Method and device for receiving and treating audiosignals in surroundings affected by noise

• US 20050276423A1
• Filed: 09/19/2001
• Published: 12/15/2005
• Est. Priority Date: 03/19/1999
• Status: Abandoned Application

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Klinke, Stefano Ambrosius, Leckschat, Dieter, Aubauer, Roland, Kern, Ralf
• Application Number:
  US09/937,022
• Publication Number:
  US 20050276423A1
• Time in Patent Office: Days
• US Class Current: 381/92
• CPC Class Codes: H04R 2201/403 Linear arrays of transducers
• CPC Class Codes: H04R 29/006 Microphone matching
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

In order to record and to process audio signals with a good useful-signal to noise-signal ratio in acoustic noise conditions and with a good ratio between the direct sound and the reflected sound in an environment which in particular has no reverberation electrical signals produced by conversion of audio signals recorded by a predetermined microphone arrangement are processed in such a manner that, if the sound pressure levels at the microphones in the microphone arrangement are the same, electrical signals which are produced by these microphones but are of different intensity—different sensitivities of the microphones—are automatically matched, without any manual matching procedures needed to be carried out individually and separately. A microphone arrangement is based on combining the characteristics of an array of microphones with those of a method for matching the sensitivity of microphones.

Claims

1-35. -35. (canceled)

36. A method for recording and processing audio signals from a sound source in an environment having acoustic noise, comprising the steps of:

(a) arranging first and second microphones with a predetermined distance between the microphones;

(b) arranging the first and second microphones with respect to a major axis defined by the first microphone in such a manner that the second microphone is arranged at a predetermined angle to the major axis and/or at a predetermined offset distance from the major axis; and

(c) processing first and second electrical signals respectively produced by the first and second microphones by automatically matching the first and second electrical signals which have different sensitivities and/or different frequency responses.

37. The method as claimed in claim 36 wherein the arranging steps further comprise arranging a plurality of second microphones relative to the first microphone, each second microphone producing a second electrical signal, and wherein the processing step further comprises processing the first electrical signal which each second electrical signal in pairs by automatically matching respectively difference sensitivities and/or frequency responses in the electrical signals produced by the microphones.

38. The method as claimed in claim 37, wherein when matching for difference sensitivities, further comprising the steps of:

(a) filtering each pair of the first electrical signal and the second electrical signal;

(b) forming signal level differences from the filtered electrical signals; and

(c) varying the respective signal levels of the unfiltered electrical signals as a function of the signal level differences until the signal level differences each essentially have a value “

0”

.

39. The method as claimed in claim 38, further comprising the steps of:

(a) forming a sum signal and a difference signal for each pair of first and second signals from the unfiltered electrical signals;

(b) forming a joint signal from the respective sum signals and difference signals in order to achieve a higher-order directional characteristic by forming linear combinations and/or propagation time delays based on the delay and sum principle; and

(c) filtering the joint signal in order to achieve a desired frequency response and a desired sensitivity.

40. The method as claimed in claim 38, further comprising the step of filtering each pair of first and second electrical signals when the major axis is arranged essentially at right angles to the sound source.

41. The method as claimed in claim 38, further comprising the step of low-pass filtering each pair of first and second electrical signals when the major axis is not arranged essentially at right angles to the sound source, and when only first and second microphones are arranged, defining a wavelength of the low-pass-filtered frequencies as greater than twice the distance between the first and second microphones, and when the first microphone and the plurality of second microphones are arranged, defining a wavelength of the low-pass-filtered frequencies as greater than a sum of the distances between the individual microphones.

42. The method as claimed in claim 37, wherein when matching different sensitivities, further comprising the steps of:

(a) measuring signal levels of both the first electrical signal and the second electrical signal for each pair of first and second electrical signals;

(b) forming signal level differences from the measured signal levels; and

(c) varying the respective signal levels of the electrical signals as a function of the signal level differences until the signal level differences each essentially have a value “

0”

.

43. The method as claimed in claim 42, further comprising the steps of:

(a) forming a sum signal and a difference signal for each pair of first and second electrical signals;

(b) forming a joint signal from the respective sum signals and difference signals in order to achieve a higher-order directional characteristic by forming linear combinations and/or propagation time delays based on a delay and sum principle; and

(c) filtering the joint signal in order to achieve a desired frequency response and desired sensitivity.

44. The method as claimed in claim 37, wherein when matching different frequency responses, further comprising the steps of:

(a) filtering the first electrical signal and the second electrical signal n times where nε

N;

(b) measuring signal levels of both the filtered first electrical signal and the filtered second electrical signal;

(c) forming signal level differences from the measured signal levels of the filtered electrical signals; and

(d) varying the respective signal levels relating to the filtering of the electrical signals as a function of the signal level differences until the signal level differences each essentially have a value “

0”

.

45. The method as claimed in claim 44, wherein the first electrical signal and the second electrical signal are bandpass-filtered n times where nε

N.

46. The method as claimed in claim 44 further comprising the steps of:

(a) forming a sum signal and a difference signal for each pair of the first electrical signal or first total signal of the n-times filtered first electrical signal, and a second total signal of the n-times filtered second electrical signal;

(b) forming a joint signal from the respective sum signals and difference signals in order to achieve a higher-order directional characteristic by forming linear combinations and/or propagation time delays based on the delay and sum principle; and

(c) filtering the joint signal in order to achieve a desired frequency response and a desired sensitivity.

47. The method as claimed in claim 37, wherein when matching different frequency responses, further comprising the steps of:

(a) filtering at least one of the first electrical signal and the second electrical signal for equalization;

(b) filtering the first electrical signal and the second electrical signal for weighting;

(c) measuring signal levels of both the weighted first electrical signal and the weighted second electrical signal;

(d) forming signal level differences from the measured signal levels of the weighted electrical signals; and

(e) varying the respective signal levels relating to the equalization filtering of the electrical signals as a function of the signal level differences until the signal level differences each essentially have a value “

0”

.

48. The method as claimed in claim 47, further comprising the steps of:

(a) forming a sum signal and a difference signal for each pair of first and second signals from the first electrical signal or from the equalized first electrical signal, and from the equalized second electrical signals;

(b) forming a joint signal from the respective sum signals and difference signals in order to achieve a higher-order directional characteristic by forming linear combinations and/or propagation time delays based on the delay and sum principle; and

(c) filtering the joint signal in order to achieve a desired frequency response and desired sensitivity.

49. The method as claimed in claim 36, wherein the step of arranging first and second microphones further comprises arranging two directional or gradient microphones.

50. The method as claimed in claim 37, wherein arranging the first microphone and the plurality of second microphones comprises the step of arranging three ball microphones.

51. The method as claimed in claim 36, wherein the predetermined angle is in the range of from about 0°

to about 40°

.

52. The method as claimed in claim 36, wherein the offset distance is less than or equal to the distance between the first and second microphones.

53. The method as claimed in claim 36, wherein the first and second microphones are arranged on an acoustic boundary surface.

54. A device for recording and processing audio signals from a sound source in an environment having acoustic noise, comprising:

(a) a microphone arrangement having at least two microphones arranged in pairs with a predetermined distance between the microphones in each a pair of microphones;

(b) a first microphone and at least one second microphone of the at least two microphones being arranged with respect to a major axis, which is defined by the first microphone, in such a manner that the at least one second microphone is arranged at a predetermined angle to the major axis and/or at a predetermined offset distance from the major axis;

(c) a first filter which filters a first electrical signal produced by the first microphone and a second electrical signal produced by the second microphone, the first and second signals having different sensitivities and/or frequency responses;

(d) means for forming signal level differences in pairs from the filtered electrical signals; and

(e) a controller connected to the means for forming signal level differences which at least partially varies the respective signal levels of the unfiltered electrical signals as a function of the signal level differences, until the signal level differences each essentially have a value “

0”

.

55. The device claimed in claim 54, further comprising:

(a) sum formation means which forms sum signals and difference signals in pairs from the unfiltered electrical signals;

(b) means for forming linear combinations and/or propagation time delays which each form a joint signal from the respective sum signals and difference signals in order to achieve a higher-order directional characteristic based on the delay and sum principle; and

(c) a second filter which filters the joint signal in order to achieve a desired frequency response and a desired sensitivity.

56. The device as claimed in claim 55, wherein the first filter is one of a low-pass, high-pass or bandpass filter, when the sound source is arranged essentially at right angles to the major axis.

57. The device as claimed in claim 56, wherein the first filter is a low-pass filter when the sound source is not arranged essentially at right angles to the major axis and a wavelength of the low-pass-filtered frequencies with the microphone arrangement having two microphones is greater than twice the distance between the microphones, and, with the microphone arrangement having more than two microphones;

is greater than the sum of the distances between the individual microphones.

65. The device as claimed in claim 54, wherein if the microphone has an integrated amplifier having an operating point which can be adjusted by external circuitry, the controller is designed in such a manner that

(a) sensitivity and/or the frequency response can be controlled via a microphone supply voltage which is obtained from the sum of a constant voltage and the product of a signal level difference signal and a gain factor, or

(b) a microphone feed impedance can be adjusted via a physical control variable, which is proportional to the product of a signal level difference signal and a gain factor, supplemented by a constant variable, in such a manner that the sensitivity and/or frequency response are controllable.

66. The device as claimed in claim 54, wherein the microphone arrangement has two directional or gradient microphones.

67. The device as claimed in claim 54, wherein the microphone arrangement has three ball microphones.

68. The device as claimed in claim 54, wherein the angle is in the range of from about 0°

to about 40°

.

69. The device as claimed in claim 54, wherein the offset distance is less than or equal to the distance between the microphones.

70. The device as claimed in claim 54, wherein the microphone arrangement is arranged on an acoustic boundary surface.

58. A device for recording and processing audio signals from a sound source in an environment having acoustic noise, comprising:

(a) a microphone arrangement having at least two microphones arranged in pairs with a predetermined distance between the microphones in each pair of microphones;

(b) a first microphone and at least one second microphone of the at least two microphones being arranged with respect to a major axis, which is defined by the first microphone, in such a manner that the at least one second microphone is arranged at a predetermined angle to the major axis and/or at a predetermined offset distance from the major axis and the first microphone;

(c) means for measuring signal levels from a first electrical signal produced by conversion by the first microphone and from a second electrical signal produced by conversion by each second microphone, with the signals having different sensitivities;

(d) means for forming signal level differences in pairs from the measured electrical signals; and

(e) a controller connected to the means for forming signal level differences which at least partially varies the electrical signals as a function of the signal level differences relating to the respective signal level, until the signal level differences each essentially have a value of “

0”

.

59. The device as claimed in claim 58, further comprising:

(a) a sum formation means which forms sum signals and difference signals in pairs from the electrical signals;

(b) means for forming linear combinations and/or propagation time delays which each form a joint signal from the respective sum signals and difference signals in order to achieve a higher-order directional characteristic based on the delay and sum principle; and

(c) a filter which filters the joint signal in order to achieve a desired frequency response and a desired sensitivity.

60. A device for recording and processing audio signals from a sound source in an environment having acoustic noise, comprising:

(a) a microphone arrangement having at least two microphones arranged in pairs with a predetermined distance between the microphones in each pair of microphones;

(b) a first microphone and at least one second microphone of the at least two microphones being arranged with respect to a major axis, which is defined by the first microphone, in such a manner that the second microphone is arranged at a predetermined angle to the major axis and/or at a predetermined offset distance from the major axis and the first microphone;

(c) filters which filter a first electrical signal produced by conversion by the first microphone and a second electrical signal produced by conversion by each second microphone, with the signals having different frequency responses n times where nε

N;

(d) means for measuring signal levels of the filtered first and second signals;

(e) means for forming signal level differences in pairs from the filtered electrical signals; and

(f) a controller connected to the means for forming signal level differences which at least partially varies the respective signal levels of the filtering of the electrical signals as a function of the signal level differences until the signal level differences each essentially have a value “

0”

.

61. The device as claimed in claim 60, wherein the filter is a bandpass filter.

62. The device as claimed in claim 61, further comprising:

(a) sum formation means which forms sum signals and difference signals in pairs from the first electrical signal or from a first total signal of the n-times filtered first electrical signal, and from a second total signal of the n-times filtered second electrical signal;

(b) means for forming linear combinations and/or propagation time delays which each form a joint signal form the respective sum signals and difference signals in order to achieve a higher-order directional characteristic based on the delay and sum principle; and

(c) a filter which filters the joint signal in order to achieve desired frequency response and a desired sensitivity.

63. A device for recording and processing audio signals from a sound source, in an environment having acoustic noise, comprising:

(a) a microphone arrangement having at least two microphones arranged in pairs with a predetermined distance between the microphones in each pair of microphones;

(b) a first microphone and at least one second microphone of the at least two microphones being arranged with respect to a major axis, which is defined by the first microphone, in such a manner that the second microphone is arranged at a predetermined angle to the major axis and/or at a predetermined offset distance from the major axis and the first microphone;

(c) equalization filters which filter a first electrical signal produced by conversion by the first microphone and a second electrical signal produced by conversion by each second microphone, with the signals having different frequency responses;

(d) weighting filters which filter the first electrical signal and the second electrical signal;

(e) means for measuring signal levels of the filtered first electrical signal and of the filtered second electrical signal;

(f) means for forming signal level differences in pairs from the filtered electrical signals; and

(g) a controller connected to the means for forming signal level differences which at least partially varies the respective signal levels of the equalization filtering of the electrical signals as a function of the signal level differences until the signal level differences each essentially have a value “

0”

.

64. The device as claimed in claim 63, further comprising:

(a) sum formation means which forms sum signals and difference signals in pairs from the first electrical signal or from the equalized first electrical signal, and from the equalized second electrical signal;

(b) means for forming linear combination and/or propagation time delays which each form a joint signal from the respective sum signals and difference signals in order to achieve a higher-order directional characteristic based on the delay and sum principle; and

(c) a filter which filters the joint signal in order to achieve a desired frequency response and a desired sensitivity.