Method and apparatus for discrimination and detection of heart sounds

• US 4,220,160 A
• Filed: 07/05/1978
• Issued: 09/02/1980
• Est. Priority Date: 07/05/1978
• Status: Expired due to Term

• Current Assignee: Clinical Systems Associates Incorporated
• Original Assignee: Clinical Systems Associates Incorporated
• Inventors: Caceres, Cesar A., Kimball, John P.
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US05/922,172
• Time in Patent Office: 790 Days
• Field of Search: 128/715, 128/701, 128/773, 179/1 ST
• US Class Current: 600/528
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R

Abstract

A method and apparatus for transposition of heart sounds to a range easily detectable by the human ear and suitable for transmission, for discrimination of low intensity or brief sounds, and for display of the heart sounds on conventional recording devices involve steps of and means for, respectively, converting the heart sounds to electrical signals having given frequency components, providing an audio frequency carrier having further frequency components, generating a transposed output representing a sum and a difference of the frequency components and the further frequency components, filtering the transposed output to remove the difference of the frequency components and further frequency components, and generating an audible representation of the heart sounds and/or displaying a visual representation thereof. As a further feature, the inventive method and apparatus provide for detection of an envelope of heart sound intensity, and provision of a visual indication of whether or not electrical signals corresponding to heart sounds are of proper signal amplitude for consistent measurement of heart sound intensity.

Claims

1. Apparatus for improving aural and visual discrimination and detection of heart sounds comprising:

a transducer means for converting said heart sounds to electrical signals,

amplifying means connected to said transducer means for amplifying said electrical signals to provide an amplifier output,

adjustable high pass filter means for receiving and filtering said amplifier output to produce a filtered output having frequency components, wherein said high pass filter means has a cutoff frequency, below which said amplifier output is attenuated and above which said amplifier output is passed,

oscillator means for providing an audio frequency carrier having frequency components,

modulator means connected to said adjustable filter means and to said oscillator means for modulating said audio frequency carrier with said filtered output so as to generate a modulator output representing a sum and a difference of said frequency components of said filtered output and said audio frequency carrier,

high pass filter means connected to said modulator means for filtering said modulator output to produce a further filtered signal representing the sum of said frequency components of said filtered output and said audio frequency carrier, and

sound intensity discriminating means connected to said adjustable high pass filter means for producing a visual display of said filtered output, whereby to provide visual detection and discrimination of inaudible heart sound events.

2. The apparatus of claim 1 wherein said oscillator means provides an audio frequency carrier having a frequency above 240 Hz, such that sum of the frequency components of said filtered output and said audio frequency carrier is within a frequency range more suitable for transmission over conventional phone lines and for discrimination by a practitioner.

3. The apparatus of claim 1 wherein said modulator means comprises a voltage multiplier.

4. The apparatus of claim 1 wherein said sound intensity discriminating means comprises:

rectifier means connected to said adjustable high-pass filter means for rectifying said filtered output to produce a rectifier output,

log amplifier means connected to said rectifier means for logarithmically amplifying said rectifier output so as to provide improved sensitivity to low level heart sounds and producing a log amplifier output,

a voltage comparator means connected to said log amplifier means for comparing said log amplifier output with adjustable threshold levels to produce a comparison output, and

display means responsive to said comparison output for providing an indication of proper signal amplitude for consistent measurement of said heart sound intensity levels.

5. The apparatus of claim 4, further comprising visual indicator means responsive to said log amplifier output for producing a visual signal that closely approximates the physiologic hearing intensity curve of the practitioner and amplifies low level sound intensity.

6. The apparatus of claim 1, wherein said adjustable high pass filter means attenuates at least one of unwanted chest movement and unwanted breathing sounds.

7. A method of detecting and discriminating heart sounds utilizing visual and aural display devices, said method comprising the steps of:

providing said visual device with an upper threshold and a lower threshold potentiometer,

frequency transposing said heart sounds to obtain a frequency-transposed heart sound,

listening to the frequency-transposed heart sound for heart sounds that may normally be inaudible,

adjusting said upper threshold potentiometer for activation of said visual device in the presence of high intensity heart sounds,

detecting an envelope of said heart sounds to produce an envelope signal,

displaying said envelope signal on said visual device so as to detect low intensity heart sounds,

adjusting said lower threshold potentiometer to present a display sharply defining timing between said heart sounds,

adjusting said lower threshold potentiometer to visually detect low intensity heart sounds that may normally be inaudible,

combining said aural and visual displays of said heart sounds to provide an accurate presentation of said timing, said heart sound intensity, and said frequency of said heart sounds, and

visually displaying said envelope of said heart sounds and discriminated sound intensity levels on said visual device.

8. Apparatus for improving aural and visual discrimination and detection of heart sounds, comprising:

input means for receiving and converting said heart sounds to electrical signals having frequency components,

oscillator means for providing an audio frequency carrier having further frequency components,

transposer means responsive to said electrical signals and to said audio frequency carrier for generating a transposer output including a sum and a difference of said frequency components and said further frequency components,

high pass filter means for filtering said transposer output to remove said difference of said frequency components and said further frequency components so as to produce a filtered output, and

output means responsive to said filtered output for generating an audible representation of said heart sounds.

9. The apparatus of claim 8, further comprising envelope detecting means responsive to said electrical signals from said input means for detecting an envelope of heart sound intensity therefrom so as to produce an envelope output, and intensity threshold detector means responsive to said envelope output for providing a visual indication having a first state for indicating when said electrical signals are of proper signal amplitude for consistent measurement of said heart sound intensity, and having a second state for indicating when said electrical signals are not of proper signal amplitude for consistent measurement of said heart sound intensity.

10. The apparatus of claim 8, wherein said transposer means comprises means for multiplying said electric signals by said audio frequency carrier.

11. Apparatus for improving aural and visual discrimination and detection of heart sounds, comprising:

input means for receiving and converting said heart sounds to electrical signals having frequency components,

oscillator means for providing an audio frequency carrier having further frequency components,

transposer means responsive to said electrical signals and to said audio frequency carrier for generating a transposer output including a sum and a difference of said frequency components and said further frequency components, and

output means responsive to said filtered output for generating an audible representation of said heart sounds;

said transposing means comprising means for single sideband modulating said audio frequency carrier by said electrical signals to produce an upper sideband output representing a sum of said frequency components.

12. A method of detecting and discriminating heart sounds, comprising the steps of:

receiving and converting said heart sounds to electrical signals, having frequency components,

providing an audio frequency carrier having further frequency components,

transposing said electrical signals in conjunction with said audio frequency carrier to generate a transposed output including a sum and a difference of said frequency components and said further frequency components,

high-pass filtering said transposed output to produce a filtered output, and

output processing said filtered output to detect and discriminate said heart sounds.

13. The method of claim 12, wherein said transposing step comprises multiplying said electrical signals by said audio frequency carrier to produce a sum and difference signal.

14. A method of detecting and discriminating heart sounds, comprising the steps of:

receiving and converting said heart sounds to electrical signals, having frequency components,

providing an audio frequency carrier having further frequency components,

transposing said electrical signals in conjunction with said audio frequency carrier to generate a transposed output, and

output processing said transposed output to detect and discriminate said heart sounds;

said transposing step comprising single sideband modulating said audio frequency carrier by said electrical signals to produce an upper sideband output representing a sum of said frequency components.