Noise rejecting electronic stethoscope

• US 7,991,165 B2
• Filed: 10/04/2006
• Issued: 08/02/2011
• Est. Priority Date: 10/04/2006
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Russotti, Joseph S., Kassal, James J.
• Primary Examiner(s): Mei; Xu
• Assistant Examiner(s): LAO, LUNSEE
• Application Number:
  US11/586,741
• Publication Number:
  US 20080137876A1
• Time in Patent Office: 1,763 Days
• Field of Search: 381/67, 381 711- 716, 381/71.8, 381/71.11, 381/150, 381/190, 181/126, 181131-132, 734/31, 735/78, 600/300, 600/534, 600/528, 600/595, 600/538
• US Class Current: 381/67
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R

Abstract

An acoustic-electronic stethoscope that filters aberrant environmental background noise. The chest piece employs acoustic vents to inhibit resonant amplification of noise and contains a diaphragm design that focuses vibrational energy to a raised ring, which transfers and further focuses the energy to a piezoelectric polymer sensor with dual elements. The ensuing electrical signal is then preamplified with the low frequency sound, comprising predominantly background noise, filtered out. The stethoscope contains a binaural head set and output jack for down loading of data. Furthermore, areas normally subject to exposure and damage to water, such as the chest piece and headset, are water-tight.

Claims

1. An electronic stethoscope comprising a chest piece having a diaphragm, operably connected to a sensor circuit board assembly, containing a top and a bottom surface and also having two piezoelectric polymer sensor elements with one mounted on and electrically connected to each of said top sensor circuit board assembly surface and the other mounted on and electrically connected to the bottom surface, such that vibrational energy impacting on said diaphragm results in dynamic strain on said piezoelectric polymer sensor elements and generation of an electrical signal to a signal output device, wherein sensor assembly contains a preamplifier circuit that provides high pass filtering that suppresses low frequency sounds below 50 Hz and that contains a difference amplifier that cancels common mode noise from the sensor assembly by subtracting the signals from said top and bottom piezoelectric polymer sensor elements.

2. The stethoscope of claim 1, wherein said sensor circuit board assembly contains grooves, wherein said grooves permit flexion of said assembly and flexion of said piezoelectric polymer sensor elements.

3. The stethoscope of claim 1, wherein said piezoelectric polymer sensor elements give rise to an electrical signal of opposite polarity when said sensor assembly is flexed.

4. The stethoscope of claim 1, wherein said signal output device is a binaural headset.

5. The stethoscope of claim 1, wherein said chest piece contains a contoured housing containing a grip for holding said chest piece.

6. The stethoscope of claim 1, wherein said chest piece contains an activation switch positioned such that pressing the chest piece to a patient causes activation of the stethoscope.

7. The stethoscope of claim 1, wherein audible feed back signals is provided to the user.

8. The stethoscope of claim 1, wherein said sensor circuit board assembly is electrically connected to a junction enclosure containing condition circuitry.

9. The stethoscope of claim 1, wherein said diaphragm is contained in a diaphragm retainer having a plurality of acoustic vent spaces around the periphery of said diaphragm retainer for the prevention of resonant amplification of sound.

10. The stethoscope of claim 1, wherein said diaphragm has a raised portion for contacting the skin and focusing vibrations.

11. The stethoscope of claim 1, wherein said diaphragm is operably connected to said sensor circuit board assembly via a coupling disk.

12. The stethoscope of claim 4, wherein said binaural head set comprises two ear assemblies with each of said assembly having an ear component containing an ear tip for insertion into the ear and an attachment component, electrically connected to said junction, and a micro-speaker in acoustic communication with the ear tip component via an airway extending lengthwise through the diameter of the assembly with said attachment component and earpiece component connected to form a water tight seal.

13. The stethoscope of claim 7, wherein said audible feed back signals are provided when the volume and band controls are used and when the batteries are low.

14. The stethoscope of claim 8, wherein said signal conditioning circuitry contains for bell and diaphragm modes.

15. The stethoscope of claim 8, wherein said signal condition circuitry contains noise-blanking circuitry with frequency-dependent sensitivity.

16. The stethoscope of claim 8, wherein said connection of said junction enclosure to said chest piece also contains an output jack such than an electrical connection to a data recording device can be made.

17. The stethoscope of claim 9, wherein said diaphragm retainer is made of a nonmetallic material.

18. The stethoscope of claim 9, wherein said chest piece is acoustically unbounded.

19. The stethoscope of claim 9, wherein said chest piece contains a seal membrane adjacent to said bottom surface of said sensor assembly forming a water-tight seal between an interior compartment of said chest piece, bounded by said seal membrane and the chest piece housing and containing within it said sensor assembly, and an exterior compartment, bounded by said diaphragm, said seal membrane and the inside periphery of said diaphragm retainer.

20. The stethoscope of claim 10, wherein said raised portion is circular.

21. The stethoscope of claim 11, wherein said coupling disk impinges on the center of the bottom surface of said sensor assembly such that energy from the diaphragm via the coupling disk causes flexion of said sensor circuit board assembly and said piezoelectric polymer sensor elements.

22. The stethoscope of claim 12, wherein compliant air is provided by air volume behind said speaker and wherein said speaker is not vented to the outside.

23. The stethoscope of claim 12, wherein said ear tips are coaxial when the headset is expanded and inserted into the ears.

24. The stethoscope of claim 12, wherein said headset is watertight.

25. The stethoscope of claim 12, wherein said ear tips are coaxial when said head set is expanded such that the tips are 13.0 cm apart.

26. The stethoscope of claim 14, wherein when said bell mode is used the high pass filter has a −

3 dB frequency cut off of 55 to 65 Hz and when said diaphragm mode is used the filter has a cut off frequency of 90 to 100 Hz.

27. The stethoscope of claim 16, wherein said output jack is watertight.