Electronic stethoscope

• US 5,825,895 A
• Filed: 07/19/1996
• Issued: 10/20/1998
• Est. Priority Date: 07/21/1995
• Status: Expired due to Term

• Current Assignee: Stetchtech Corporation
• Original Assignee: Stethtech Corporation
• Inventors: Steinhubel, Daniela, Purbrick, John A., Stark, Peter R. H., Winston, David E., Grasfield, James A.
• Primary Examiner(s): Isen, Forester W.
• Application Number:
  US08/685,451
• Time in Patent Office: 823 Days
• Field of Search: 381/67, 600/508, 600/509, 600/513, 600/528, 600/586
• US Class Current: 381/67
• CPC Class Codes: A61B 7/003 Detecting lung or respiration noise
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R

Abstract

An electronic stethoscope having several modes of operation to process acoustic signals to provide filtered signals useful for diagnosis. In one mode of operation the stethoscope substantially provides only acoustic signals generated by biological activity of the heart. In another mode of operation, the acoustic stethoscope substantially provides only acoustic signals generated by biological activity of the lungs. In another mode of operation, the electronic stethoscope disproportionately amplifies abnormal heart sounds and normal heart sounds to enhance diagnosis of heart abnormalities. The electronic stethoscope is operated in a manner similar to a conventional acoustic stethoscope and has similar spectral characteristics, thus allowing a user with acoustic stethoscope experience to easily use the electronic stethoscope.

Claims

1. An electronic stethoscope, comprising:

a first transducer for converting acoustic signals into electronic signals;

a processing section, having an input coupled to an output of the first transducer, for processing the electronic signals to provide selected electronic signals representative of only selected ones of the acoustic signals; and

a second transducer, coupled to an output of the processing section, for converting the selected electronic signals into acoustic signals;

wherein the processing section operates in a murmur enhancement mode, in which the electronic signals from the output of the first transducer are processed by an automatic gain control circuit and a lowpass filter;

wherein the automatic gain control circuit has a time constant in the range of approximately 5 to 100 milliseconds.

2. The electronic stethoscope of claim 1, further comprising a bandpass filter coupled between the output of the first transducer and the input of the processing section.

3. The electronic stethoscope of claim 1, wherein the processing section can also operate in a normal operational mode in which the electronic signals from the output of the first transducer are transmitted substantially unchanged to the second transducer.

4. The electronic stethoscope of claim 1, wherein the processing section can also operate in a respiratory mode, in which the electronic signals from the output of the first transducer are filtered by a highpass filter before being transmitted to the second transducer.

5. The electronic stethoscope of claim 4, wherein the highpass filter has a corner frequency in the range of 100 to 300 Hz.

6. The electronic stethoscope of claim 1, wherein the processing section can also operate in a cardiac mode in which the electronic signals from the output of the first transducer are filtered by the lowpass filter before being transmitted to the second transducer.

7. The electronic stethoscope of claim 6, wherein the first lowpass filter has a corner frequency in the range of 400 to 600 Hz.

8. The electronic stethoscope of claim 2, wherein the bandpass filter has a passband in the range of 20 Hz to 1600 Hz.

9. The electronic stethoscope of claim 5, wherein the corner frequency is approximately 140 Hz.

10. The electronic stethoscope of claim 1, further comprising an output amplifying section coupled between the output of the processing section and the second transducer.

11. The electronic stethoscope of claim 1, further comprising an indicator for providing status of a power supply for the electronic stethoscope.

12. The electronic stethoscope of claim 11, wherein the indicator is a visual indicator.

13. The electronic stethoscope of claim 11, wherein the indicator is an audible indicator.

14. The electronic stethoscope of claim 1, wherein the electronic signals are processed by the automatic gain control circuit and then transmitted to the first lowpass filter.

15. The electronic stethoscope of claim 1, wherein the response time constant is approximately 10 milliseconds.

16. The electronic stethoscope of claim 1, further comprising a transceiver, coupled between an output of the first transducer and the input of the processing section, for transmitting electronic signals from the first transducer and receiving electronic signals to be processed by the processing section.

17. The electronic stethoscope of claim 16, wherein the transceiver is an infrared transceiver.

18. The electronic stethoscope of claim 16, wherein the transceiver is a radio frequency transceiver.

19. The electronic stethoscope of claim 7, wherein the corner frequency is approximately 480 Hz.

20. The electronic stethoscope of claim 1, further comprising means for changing at least one operational parameter of the processing section to change the selected electronic signals.

21. The electronic stethoscope of claim 1, further comprising a transceiver for transmitting signals from the stethoscope and for receiving signals to be processed by the stethoscope.

22. The electronic stethoscope of claim 1, further comprising a transmitter, coupled between an output of the first transducer and the input of the processing section, for transmitting electronic signals from the first transducer.

23. The electronic stethoscope of claim 1, further comprising a subsonic filter coupled between an output of the first transducer and the input of the processing section.

24. The electronic stethoscope of claim 1, further comprising an input limiter, coupled between an output of the subsonic filter and the input of the processing section, that limits a magnitude of the electronic signals provided to the processing section.

25. The electronic stethoscope of claim 1, further comprising a receiver, coupled between an output of the first transducer and the input of the processing section, for receiving electronic signals to be processed by the processing section.

26. The electronic stethoscope of claim 1, wherein the processing section includes at least one filter having a controllable corner frequency.

27. The electronic stethoscope of claim 26, wherein the processing section includes control circuitry for varying the corner frequency.

28. The electronic stethoscope of claim 27, wherein the control circuitry increases the corner frequency.

29. The electronic stethoscope of claim 27, wherein the control circuitry decreases the corner frequency.

30. The electronic stethoscope of claim 27, wherein the processing section includes a plurality of filters having respective controllable corner frequencies.

31. The electronic stethoscope of claim 30, wherein the control circuitry varies the corner frequencies of each filter in the plurality of filters independently.

32. The electronic stethoscope of claim 26, wherein the at least one filter is a digital filter.

33. The electronic stethoscope of claim 26, wherein the at least one filter is an analog filter.

34. An electronic stethoscope, comprising:

a first transducer for converting acoustic signals into electronic signals;

a processing section, having an input coupled to an output of the transducer, for processing the electronic signals to provide selected electronic signals representative of only selected ones of the acoustic signals; and

a second transducer, coupled to an output of the processing section, for converting the selected electronic signals into acoustic signals;

wherein the processing section operates in a murmur enhancement mode, in which the electronic signals from the output of the first transducer are processed by a variable gain amplifier, a threshold limiter, and a lowpass filter.

35. A method of filtering acoustic signals generated by biological activity to substantially isolate a selected acoustic signal generated by a particular organ from the acoustic signals, the method comprising the steps of:

converting acoustic signals generated by biological activity into electronic signals;

selectively filtering the electronic signals to provide a filtered electronic signal that contains substantially only electronic signals representative of acoustic signals generated by a particular organ;

amplifying to a determined level, using a first gain, a first group of electronic signals representative of normal cardiac sounds;

amplifying to the predetermined level, using a second gain, a second group of electronic signals representative of abnormal cardiac sounds;

wherein the first and second gains are varied one to the other or vice versa with a time constant in the range of approximately 5 to 100 milliseconds;

lowpass filtering the electronic signal;

so that the filtered electronic signal contains substantially only electronic signals representative of normal and abnormal cardiac sounds; and

converting the filtered electronic signal into an audible acoustic signal.

36. The method of claim 35, wherein the step of selectively filtering can also comprise a step of highpass filtering the electronic signals so that the filtered electronic signal contains substantially only electronic signals representative of acoustic signals generated by lungs.

37. The method of claim 35, wherein the biological activity is animal biological activity.

38. The method of claim 35, wherein the time constant is approximately 10 milliseconds.

39. The method of claim 35, wherein the biological activity is human biological activity.

58. The method of any one of claims 35, 49, or 50 further comprising the step of controlling a volume of the audible acoustic signal.

40. An electronic stethoscope, comprising:

a first transducer for converting acoustic signals into electronic signals;

a processing section, having an input coupled to an output of the first transducer, for processing the electronic signals to provide selected electronic signals representative of only selected ones of the acoustic signals; and

a second transducer, coupled to an output of the processing section, for converting the selected electronic signals into acoustic signals;

further comprising an output amplifying section coupled between the output of the processing section and the second transducer;

wherein the output amplifying section includes a summing circuit having an input coupled to an output of the processing section, a lowpass filter having an input coupled to an output of the summing circuit, a volume control circuit having an input coupled to an output of the low pass filter, an output volume limit circuit having an input coupled to an output of the volume control circuit, and a driver amplifier having an input coupled to an output of the output volume limit circuit and an output coupled to the second transducer.

41. The electronic stethoscope of claim 40, wherein the second lowpass filter has a corner frequency in the range of 1500 Hz to 1700 Hz.

42. An electronic stethoscope comprising:

a first transducer for converting acoustic signals into electronic signals;

a processing section, having an input coupled to an output of the first transducer, for processing the electronic signals to provide selected electronic signals representative of only selected ones of the acoustic signals; and

a second transducer, coupled to an output of the process section, for converting the selected electronic signals into acoustic signals

wherein the processing section includes a first circuit that transmits the electronic signals substantially unchanged, a second circuit including a highpass filter that transmits electronic signals above approximately 100 Hz, a third electronic circuit including a lowpass filter that transmits electronic signals below approximately 600 Hz, a fourth electronic circuit including an automatic gain control circuit having a time constant in the range of approximately 5 to 100 milliseconds, coupled to the lowpass filter, that amplifies and transmits electronic signals below approximately 600 Hz, and a switching section that selects one of the first, second, third, or fourth circuits; and

further comprising a control section that controls the switching section to select one of the first, second, third, or fourth circuits.

43. The electronic stethoscope of claim 42, wherein the control section further comprises:

a plurality of switches; and

a switch decoder having an input coupled to the plurality of switches and an output coupled to the switching section, wherein the switching section selects one of the first, second, third, or fourth circuits in response to activation of one switch in the plurality of switches.

44. The electronic stethoscope of claim 42, further comprising an adjustable clock/oscillator circuit that produces a control signal that varies a corner frequency of the highpass filter and that varies a corner frequency of the lowpass filter.

59. The electronic stethoscope of any one of claims 58, 42, 46, 48, 53, wherein the time constant is approximately 10 milliseconds.

45. An electronic stethoscopes, comprising:

a first transducer for converting acoustic signals into electronic signals;

a processing section, having an input coupled to an output of the first transducer, for processing the electronic signals to provide selected electronic signals representative of only selected ones of the acoustic signals; and

a second transducer, coupled to an output of the processing section, for converting the selected electronic signals into acoustic signals;

wherein the processing section operates in a murmur enhancement mode, in which the electronic signals from the output of the first transducer are processed by an automatic gain control circuit, a logorithmic compressor, and a lowpass filter.

46. An electronic stethoscope, comprising:

a first transducer for converting acoustic signals generated by human biological activity into electronic signals;

a signal processor, having an input that receives the electronic signals, for processing the electronic signals to provide selected electronic signals representative of acoustic signals generated by a selected human organ; and

a second transducer, coupled to an output of the signal processor for converting the selected electronic signals into audible acoustic signals;

wherein the electronic stethoscope has a mode of operation in which the audible acoustic signals include normal cardiac sounds and abnormal cardiac sounds, wherein only one of the normal and abnormal cardiac sounds are substantially amplified;

wherein the signal processor includes an automatic gain control circuit, having a time constant in the range of approximately 5 to 100 milliseconds, coupled to a lowpass filter.

47. An electronic stethoscope, comprising:

a first transducer for converting acoustic signals generated by human biological activity into electronic signals;

a signal processor, having an input that receives the electronic signals, for processing the electronic signals to provide selected electronic signals representative of acoustic signals generated by a selected human organ; and

a second transducer, coupled to an output of the signal processor for converting the selected electronic signals into audible acoustic signals;

wherein the electronic stethoscope has a mode of operation in which the audible acoustic signals include normal cardiac sounds and abnormal cardiac sounds, wherein only one of the normal and abnormal cardiac sounds are substantially amplified;

wherein the signal processor includes a lowpass filter and a variable gain amplifier having an output coupled to an input of a threshold limiter.

48. An electronic stethoscope, comprising:

a first transducer for converting acoustic signals generated by human biological activity into electronic signals;

a signal processor, having an input that receives the electronic signals, for processing the electronic signals to provide selected electronic signals representative of acoustic signals generated by a selected human organ; and

a second transducer, coupled to an output of the signal processor for converting the selected electronic signals into audible acoustic signals;

wherein the electronic stethoscope has a mode of operation in which the audible acoustic signals include normal cardiac sounds and abnormal cardiac sounds, wherein only one of the normal and abnormal cardiac sounds are substantially amplified;

wherein the signal processor includes a lowpass filter and an automatic gain control circuit, having a time constant in the range of approximately 5 to 100 milliseconds, having an output coupled to an input of a logorithmic compressor.

49. A method of filtering acoustic signals generated by biological activity to substantially isolate a selected acoustic signal generated by a particular organ from the acoustic signals, the method comprising the step of:

converting acoustic signals generated by biological activity into electronic signals;

selectively filtering the electronic signals to provide a filtered electronic signal that contains substantially only electronic signals representative of acoustic signals generated by a particular organ; and

converting the filtered electronic signal into an audible acoustic signal;

wherein the step of selectively filtering comprises the steps of;

amplifying the electronic signals by a predetermined gain;

limiting particular ones of the amplified electronic signals from further amplification; and

lowpass filtering the limited, amplified electronic signals;

so that the filtered electronic signal contains substantially only electronic signals representative of normal and abnormal cardiac sounds.

50. A method of filtering acoustic signals generated by biological activity to substantially isolate a selected acoustic signal generated by a particular organ from the acoustic signals, the method comprising the steps of:

converting acoustic signals generated by biological activity into electronic signals;

selectively filtering the electronic signals to provide a filtered electronic signal that contains substantially only electronic signals representative of acoustic signals generated by a particular organ; and

converting the filtered electronic signal into an audible acoustic signal;

wherein the step of selectively filtering comprises the steps of;

amplifying the electronic signals to a predetermined level;

logorithmically compressing the amplified electronic signals; and

lowpass filtering the logorithmically compressed electronic signals;

so that the filter electronic signal contains substantially only electronic signals representative of normal and abnormal cardiac sounds.

51. An electronic stethoscope, comprising:

a first transducer for converting acoustic signals into electronic signals;

a processing section, having an input coupled to an output of the first transducer, for processing the electronic signals to provide selected electronic signals representative, of only selected ones of the acoustic signals; and

a second transducer, coupled to an output of the processing section, for converting the selected electronic signals into acoustic signals;

further comprising a subsonic filter coupled between an output of the first transducer and the input of the processing section;

wherein the subsonic filter is a second order Bessel highpass filter having a corner frequency in the range of 30 to 40 Hz.

52. The electronic stethoscope of claim 51, wherein the corner frequency is approximately 35 Hz.

53. An electronic stethoscope, comprising:

a first transducer for converting acoustic signals into electronic signals;

a processing section, having an input coupled to an output of the first transducer, for processing the electronic signals to provide selected electronic signals representative of only selected ones of the acoustic signals; and

a second transducer coupled to an output of the processing section, for converting the selected electronic signals into acoustic signals;

wherein the processing section includes a first circuit that transmits the electronic signals substantially unchanged, a second circuit including a highpass filter that transmits electronic signals above approximately 100 Hz, a third electronic circuit including a lowpass filter that transmits electronic signals below approximately 600 Hz, a fourth electronic circuit including an automatic gain control circuit, having a time constant in the range of approximately 5 to 100 milliseconds, coupled to the lowpass filters, that amplifies and transmits electronic signals below approximately 600 Hz, and a switching section that selects one of the first, second, third, or fourth circuits; and

a microcontroller that controls the switching section to select one of the first, second, third, or fourth circuits.

54. The electronic stethoscope of claim 53, wherein the microcontroller includes a memory for storing a reference biological signal and controls playback of the reference biological signal in response to user input.

55. The electronic stethoscope of claim 53, wherein the microcontroller controls a volume of an audio signal provided by the electronic stethoscope by providing a control signal to control a gain of an amplifier circuit.

56. The electronic stethoscope of claim 53, wherein the microcontroller responds to a pulse encoder to vary a corner frequency of at least one filter in the processing section.

57. The electronic stethoscope of claim 56, wherein the processing section includes a plurality of filters having respective controllable corner frequencies and the microcontroller comprises means for varying the corner frequencies of each filter in the plurality of filters independently.

60. An electronic stethoscope, comprising:

a first transducer for converting acoustic signals generated by human biological activity into electronic signals;

a signal processor, having an input that receives the electronic signals, for processing the electronic signals to provide selected electronic signals representative of acoustic signals generated by a selected human organ; and

a second transducer, coupled to an output of the signal processor for converting the selected electronic signals into audible acoustic signals;

wherein the signal processor includes a first circuit that transmits the electronic signals substantially unchanged, a second circuit including a highpass filter that transmits electronic signals above approximately 100 Hz, a third electronic circuit including a lowpass filter that transmits electronic signals below approximately 600 Hz, a fourth electronic circuit including an automatic gain control circuit having a time constant in the range of approximately 5 to 100 milliseconds coupled to the lowpass filter that amplifies and transmits electronic signals below approximately 600 Hz, and a switching circuit that selects one of the first, second, third, or fourth circuits; and

further comprising a control circuit that controls the switching circuit to select one of the first, second, third, or fourth circuits.

61. The electronic stethoscope of claim 60, further comprising a bandpass filter coupled between the first transducer and the signal processor for transmitting only those electronic signals within an audible frequency range.

62. The electronic stethoscope of claim 61, wherein the audible frequency range is approximately 20 Hz to 1600 Hz.

63. The electronic stethoscope of claim 60, wherein the electronic stethoscope has a mode of operation in which the audible acoustic signals are substantially unchanged by the signal processor.

64. The electronic stethoscope of claim 60, wherein the electronic stethoscope has a mode of operation in which the audible acoustic signals are substantially respiratory sounds only.

65. The electronic stethoscope of claim 60, wherein the electronic stethoscope has a mode of operation in which the audible acoustic signals are substantially cardiac sounds only.

66. The electronic stethoscope of claim 60, wherein the electronic stethoscope has a mode of operation in which the audible acoustic signals include normal cardiac sounds and abnormal cardiac sounds, wherein only one of the normal and abnormal cardiac sounds are substantially amplified.

67. The electronic stethoscope of claim 60, wherein the control section further comprises:

a plurality of switches;

a switch decoder having an input connected to the plurality of switches and an output connected to the switching circuit, wherein the switching circuit selects one of the first, second, third, or fourth circuits in response to the activation of one switch in the plurality of switches.

68. The electronic stethoscope of claim 60, further comprising an adjustable clock/oscillator circuit that produces a control signal that varies a corner frequency of the highpass filter and that varies the corner frequency of the lowpass filter.