Electronic stethoscope

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.