Sound monitoring apparatus

• US 4,528,689 A
• Filed: 12/07/1983
• Issued: 07/09/1985
• Est. Priority Date: 09/22/1981
• Status: Expired due to Term

• Current Assignee: IAI Limited Partnership
• Original Assignee: International Acoustics Incorporated
• Inventors: Katz, Hart V.
• Primary Examiner(s): Rubinson, Gene Z.
• Assistant Examiner(s): Byrd, Danita R.
• Application Number:
  US06/558,746
• Time in Patent Office: 580 Days
• Field of Search: 381/67, 381/56, 381/31, 381/32, 381/68, 381/34, 381/38, 179/107 R, 360/8, 360/32, 128/715
• US Class Current: 381/67
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R
• CPC Class Codes: G01H 3/00 Measuring characteristics of vibrations by using a detector in a fluid G01H7/00, G01H9/00, G01H11/00 take precedence

Abstract

Sound monitoring apparatus is described which provides a slowed down version of the original sound, e.g. a heart beat without changing the quality of the sound as perceived by a trained listener such as a physician. The amount by which the sound is slowed down can be varied by the user. The original sound is converted to an analog electrical signal, digitized and electronically processed in a microprocessor-based circuit such that digital data corresponding to cycles of the analog signal are stored in a random access memory. The microprocessor reads out the digital data a predetermined number of times corresponding to a number of sound cycles according to the rate set by the physician. The digital data is reconstituted into sound which is composed of replicated sets of cycles of the original sound. The repetition rate of the heart-beat in the output sound is a fraction of the repetition of the heart-beat in the original sound but the sound quality appears the same to the physician as the pitch is invariant. In a preferred embodiment stored digital data corresponding to each input half signal is duplicated and data corresponding to the duplicated positive half-cycle is inverted to give data corresponding to a negative half-cycle and the non-duplicated negative half-cycle data is inverted to give a positive half-cycle data. In another embodiment, the signal processing circuitry is incorporated into a conventional stethoscope and the circuitry is implemented using low power CMOS technology. The invention has application in other fields such as vibration analysis.

Claims

1. Sound processing and monitoring apparatus for processing an original sound and providing a sound output therefrom such that that sound output is recognizable as a slowed down version of the original sound at the same pitch, the apparatus comprising,

first sound transducer means for producing a cyclically varying analog input signal in response to an input sound;

analog to digital (A/D) converting means connected to said first sound transducer means for converting said analog input signal into a digital input signal;

memory means associated with said A/D converting means for storing said digital signal therein;

control means connected to said memory means for controlling the storage of said digital signal in said memory means, and for causing stored digital data corresponding to each respective analog input half-cycle to be read out of said memory means a predetermined multiple number of times to form a digital output signal;

said control means constituting means effective for controlling the phase of the output;

digital to analog (D/A) converting means for converting said digital output signal into an analog output signal, said analog output signal being composed of groups of said predetermined multiple number of half-cycles, each group corresponding to at least one half-cycle of said analog input signal; and

second sound transducer means connected to the output of said D/A converter for producing an output sound in response to said analog output signal, said output sound being recognizable as a slowed down version of said input sound with the same pitch.

2. Sound monitoring apparatus as claimed in claim 1, wherein each group corresponds to a full cycle of said analog input signal including means for varying the number of times digital data is read out from the memory means.

3. Sound monitoring apparatus as claimed in claim 2 wherein said control means is a microprocessor and said memory means is a random access memory.

4. Sound monitoring apparatus as claimed in claim 3 wherein the means for varying is a switch which is directly connected to said microprocessor, said means being manually adjustable.

5. Sound monitoring apparatus as claimed in claim 4 including low pass filter means connected between the sound transducer means and the A/D converter.

6. Sound monitoring apparatus as claimed in claim 4 wherein the memory capacity of the random access memory is such that digital data corresponding to at least six seconds can be stored therein.

7. Sound monitoring apparatus as claimed in claim 6 wherein the A/D converting means, memory means, microprocessor and D/A converting means are implemented by complementary-metaloxide semiconductor (CMOS) technology.

8. Sound monitoring apparatus as claimed in claim 1 wherein the control means counts the number of times said digital data crosses a reference value to determine when said digital data is read out from the memory.

9. Sound monitoring apparatus as claimed in claim 8 wherein the reference value is a zero voltage level.

10. Sound monitoring apparatus as claimed in claim 9 wherein said apparatus is incorporated into a stethoscope having a bell and binaural earpieces, said microphone means being located in proximity to the bell and said loudspeaker means being located in said stethoscope so as to transmit the sound in response to the analog output signal to the binaural earpieces.

11. Sound monitoring apparatus as claimed in claim 1 wherein the A/D and D/A connecting means are contained in the same physical device.

12. Sound monitoring apparatus as claimed in claim 1 wherein said control means splits data of a cycle into half cycles determined by the zero crossing, and causes data corresponding to a positive half cycle to be read out to give a positive output half cycle, then causes said data to be inverted and read out again to give a negative half cycle which is equivalent to the positive half cycle inverted about the zero axis, then causing data corresponding to a negative half cycle to be read out and inverted to give a positive half cycle then caused data corresponding to the negative half cycle to be read out again such that adjacent half cycles in said output signal are inverted about said zero axis such that the cross-over between each adjacent pair of half cycles is substantially smooth.

13. Sound monitoring and processing apparatus as claimed in claim 1, wherein said control means constitutes means for controlling the polarity of the output cycles.

14. An electronic stethoscope for processing an original sound such that the sound output is recognizable as a slowed down version of the original sound at the same pitch, the stethescope comprising sound collection means for location at a source of sound, conduit means having an end connected to said collection means for collecting and transmitting an input sound, electronic signal processing means connected to the other end of the conduit means for receiving the transmitted sound, the received sound being formed by an input transducer into an input signal for said electronic processing means, bifurcated conduit means connected with an output of said electronic processing means, an earpiece means connected to each of the distal ends of said bifurcated conduit, said bifurcated conduit being adapted to receive electronically processed signals from said electronic signal processing means, said electronic signal processing means including analog to digital (A/D) converting means for converting an analog input signal into a digital signal, memory means associated with said analog to digital converting means for storing said digital signal therein control means associated with said memory means for reading out said stored digital data corresponding to each respective analog input cycle a predetermined multiple number of times, digital to analog converting means for providing an analog output signal corresponding to the digital data read out from said memory means, and sound transducer means for converting said analog output signal into an output sound, said output sound travelling along said bifurcated conduit to said earpiece means, and being recognizable as a slowed down version of the input sound with the same pitch.

15. An electronic stethoscope as claimed in claim 14 wherein said electronic processing means includes means for controlling the number of times said digital data is read out from the memory means.

16. An electronic stethoscope as claimed in claim 15 wherein means for varying the number of times said digital data is read out from said memory means is a switch directly connected to said control means and being manually operable.

17. An electronic stethoscope as claimed in claim 16 wherein said electronic processing means is located in a housing, said housing being connectable to said conduit means at one end and being connected to said bifurcated conduit at the other end, the switch being located on the housing and including a pointer and a scale to facilitate setting the number of times said digital data is to be read out from said memory means.

18. An electronic stethescope as claimed in claim 14 wherein said sound collection means is a bell.

19. In a stethescope having pickup bell means for location at a source of sound and for collecting sound emanating from said source to provide an input sound signal composed of cycles, conduit means having one end connected to the bell means and the other end bifurcating to form two separate conduit means, earpiece means located at the distal ends of said bifurcated conduit means, said conduit means guiding said sound collected by said bell means and transmitting it via said bifurcated conduit means to said earpiece means, the improvement comprising:

an electronic signal processing means in the acoustic pathway between said bell means and said earpiece means, in which the electronic signal processing means is mounted, and having a port connected to one end of said conduit means and another port connected to said bifurcated conduit means, said electronic signal processing means processing said input sound signal to provide an output sound signal, in which each respective input sound cycle is repeated a predetermined multiple number of times to form a set of cycles, said output signal being composed of successive sets of such cycles, said output sound signal being recognizable with the same pitch such that the pitch appears to be the same as the input sound signal but is reproduced at a slower rate, said slower rate being a function of the number of times each of said input signals is repeated.

20. A method of processing a cyclically varying input sound signal to produce an output sound signal which is recognizable as a slowed-down version of the input sound signal;

comprising the steps of,

(a) converting said sound wave into a cyclically varying electrical analog input signal, each signal having a positive half-cycle and a negative half-cycle,

(b) converting said analog input signal into groups of digital data, each group corresponding to one half-cycle of the analog input signal,

(c) storing said groups of digital data in a memory means,

(d) in accordance with a signal from a controller, reading out a first group of digital data values corresponding to a first positive half-cycle and converting said group of digital data values to an analog first positive half-cycle output signal,

(e) again reading out said first group of digital data values corresponding to said first positive half-cycle and inverting said digital data values to negative values,

(f) converting said negative data values to an analog first negative half-cycle output signal,

(g) reading out a second group digital data values from the memory means corresponding to a first negative half-cycle being read out and inverting said negative data to positive data values, and converting said positive data values to a second positive half-cycle output signal,

(h) again reading out from the memory means said second group of data values corresponding to the first negative half-cycle and converting said negative data values to an analog second negative half-cycle output signal,

repeating the above steps (d)-(h) for successive groups of data values stored in the memory corresponding to stored half-cycles of the analog input signal,

converting said analog electrical output signals to an output sound signal, which is recognizable as a slowed down version of the input sound signal.

21. A method of processing a cyclically varying sound wave each cycle having positive and negative half cycles comprising the steps of,

converting the cyclically varying sound wave into an electrical analog input signal,

converting the electrical analog input signal into groups of digital data each group corresponding to one half cycle of the analog input signal,

storing said groups of data in memory means in accordance with the signal from a controller reading out each group of data at least three times,

when each group of data requires to be read out an even number of times from said memory means reading out data corresponding to each positive half cycle and inverting even numbered groups of data to give negative data values,

reading out data corresponding to each negative half cycle and inverting odd numbered groups of data to give positive data values,

converting said read out data values to an electrical analog output signal,

when each group of data requires to be read out an odd number of times from said memory means reading out data corresponding to each positive half cycle and inverting even numbered groups to give negative data values then reading out data corresponding to each negative half cycle and inverting even numbered groups of data to give positive data values,

converting said read out data values to an electrical analog output signal,

converting said electrical analog output signal to an output sound wave, the frequency of the output sound wave being at least three times the frequency of the input wave.

22. A method as claimed in claim 21 wherein the groups of data are read out from the memory means three to five times.

23. A method producing a slowed down sound wave from an original cyclically varying sound wave comprising the steps of:

converting the cyclically varying sound wave into a cyclically varying analog input signal, each signal having a positive half-cycle and a negative half-cycle,

converting said half-cycle into respective groups of digital data,

storing each group of said digital data groups in a memory in accordance with a signal from a controller,

reading out each group of data from the memory successively at least three times,

inverting the data of each alternate half-cycle data group each subsequent time it is read out,

converting said read out data to an electrical analog output signal,

converting said electrical analog output signal to an output sound signal which is recognizable as a slowed down version of the input sound signal with the same pitch.

24. A heart sound analyzer for processing an original sound such that that sound output is recognizable as a slowed down version of the original heart sound at the same pitch, the analyzer comprising,

first sound transducer means for producing a cyclically varying analog input signal in response to an input heart sound;

analog to digital (A/D) converting means connected to said sound transducer means for converting said analog input signal into a digital input signal;

memory means associated with said A/D converting means for storing said digital input signal therein;

control means for controlling the storage of said digital input signal in said memory means, and for causing stored digital data corresponding to each respective analog input half-cycle to be read out of said memory means a predetermined multiple number of times to form a digital output signal;

said control means constituting means effective to split the data of a single cycle into half-cycle determined by a zero-crossing procedure, said control means causing data corresponding to a positive half-cycle to be read out successively to give a positive output half-cycle, then causing said data to be inverted and read out again to give a negative half-cycle which is equivalent to the positive half-cycle mirrored about the zero axis, said control means then causing data corresponding to a negative half-cycle to be read out, inverted to give a positive half-cycle and then causing said same data to be read out again corresponding to the negative half-cycle such that each half-cycle in said output signal is mirrored about said zero axis such that the crossover between each adjacent pair of half-cycles is substantially smooth.

25. A heart sound analyzer as claimed in claim 24 wherein said half-cycles are read out a predetermined number of times and adjacent half-cycles having opposite polarity and being read out such that the analog output signal is composed of cycles which are of laternate polarity and which have a substantially smooth transition from one half-cycle to the next when crossing the zero axis.