Wireless Auscultation Device for Continuous
Monitoring of Heart Sounds
Danielle Manley | Stephen Krammin | Mateusz Koper
Department of Biomedical Engineering
Lawrence Technological University
Faculty Advisors: Dr. Gerald LeCarpentier & Dr. Mansoor Nasir
Technical Advisor: Professor Kenneth Cook
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Auscultation: Act of listening to body sounds as a part of making a medical diagnosis
● Occurs during almost all hospital visits
● Auscultate heart, lungs, intestinal sounds
● Evaluate certain sound characteristics: o Frequency o Intensity o Duration
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● Heart Sounds o Blood flow through the heart valves o Frequency range from 20-650 Hz o Abnormal sounds interpreted as potential murmurs
● Most common murmurs: o Regurgitation o Stenosis
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Mechanical Stethoscope:
Cheap $15-100
No Power Necessary
Poor Sound Quality
Excess outside noise
Not Handsfree
Electrical Stethoscopes
Filter Noise
Amplify Sounds
Expensive $250-1000
Power Necessary
Not Handsfree
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Problem: Stethoscopes do not monitor sounds continuously and they are not hands free
Continuous heart sound monitoring would be very useful for the following applications:
● Diagnose Patients with Infectious Diseases
● Pharmaceutical Interventions
● Multiple Patient Monitoring
● Telemedicine
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● Wireless auscultation device
● Remove need for physician’s presence
● Create Bluetooth capable device
● Untethered
● Low-power
● Low-cost
● User Friendly
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● Used a cheap stethoscope head and PVC tubing
● Placed an electret condenser microphone into end of tubing
● Two wires connected from microphone to circuit’s input and ground
Microphone
Placement
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Microphone
Bias Network
HPF
LPF
Signal Amplification
Voltage Offset
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High Pass: 15 Hz
Low Pass: 964 Hz
Bandwidth:
15 Hz - 964 Hz
Gain = 75
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● Arduino Uno microcontroller with SD card shield
● Arduino program developed: o Sampling frequency of
1000 points/sec o Analog voltages read and converted to bytes (0-1023) o Data stored into a text file created on the SD card
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● Laptop paired to Bluetooth device (HC-05 Transceiver)
● Similar program developed in MATLAB o SD card read and Bluetooth transfer of data into MATLAB o Bytes converted to voltages and stored into an array
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● Matlab: o Plotting o Fast-Fourier Transform (FFT)
 Frequency components o Digital filtering
 Signal processing toolbox o Audio playback
 Sound function
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CH #2
CH #1
Biopac Electronic
Stethoscope
Signal Cable Auscultation Circuitry Biopac Display
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Our Stethoscope vs Biopac Stethoscope
● First peak - S1 heart sound (“Lub”)
● Second peak - S2 heart sound (“Dub”)
Red = Our Stethoscope
Blue = Biopac Stethoscope
● Similar results support our device functionality
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● Our device is capable of depicting healthy and abnormal heartbeats
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● Seems like Arduino is collecting more noise than Biopac
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● Seems like Arduino is collecting more noise than Biopac
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Biopac vs Arduino: Filtered Talking
● Signal is much cleaner compared to unfiltered talking
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● Wireless prototype created that can collect and send heart sounds using Bluetooth
● MATLAB program developed that can process and playback captured heart sounds
● Our device can compete with both mechanical and electrical stethoscopes in terms of: o Ease of use o Sound quality o Cost
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● Test sound isolation materials
● Miniaturize device
● Incorporate adhesive
● Central monitoring system
● Other body sounds
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● Printed Circuit Board
● Piezoelectric Transducer
● Smaller Batteries
● Mini Microcontroller
Estimated price of our stethoscope ≈ $50
(Mechanical: $15+ Electronic: $250+)
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Faculty Advisors:
● Dr. Gerald LeCarpentier: o Arduino Programming o Providing Arduino Uno
● Dr. Mansoor Nasir: o Matlab Programming o Providing Various Materials
Technical Advisor:
● Professor Kenneth Cook: o Circuit Development & Testing o Providing Various Materials
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● http://www.electronics-lab.com/blog/?p=20744
● https://www.circuitsathome.com/products-page/power-supplies/3-3v-to-
5v-600ma-dc-dc-converter-bare-pcb
● http://www.explainthatstuff.com/piezoelectricity.html
● http://www.cdc.gov/nchs/data/nhsr/nhsr007.pdf
● http://www.audiologyonline.com/articles/amplified-stethoscope-optionsfor-professionals-860
● http://www.nlm.nih.gov/medlineplus/ency/article/002226.htm
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● ECG provides insight into the electrical activity of the heart o Used primarily to determine arrhythmias
● Heart sounds provide insight on the structure o Health of heart valves o Thickening of ventricular septum o Fluid build up in pericardium
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