Stethoscopes are in use for more than 200 years for medical diagnostics, especially for auscultation in the healthcare domain. Recently, unprecedented growth in mobile technology has revived the use of stethoscopes for Telehealthcare. Digital or electronic stethoscopes are increasingly researched for use in Telehealthcare within the healthcare domain. Cardiovascular diseases have become highly prevalent worldwide, especially in the subcontinent. Improvements in diagnostics will improve the quality of life and prevent the loss of life. This research paper mainly focuses on the acoustical and multiphysics design aspects of the stethoscope for improved acoustical performance. A COMSOL model of the stethoscope chest piece was developed. The model was setup to investigate the effects of geometry, material of construction, noise and input pressure. The sound transmission efficiency of the components was investigated with multiphysics models by coupling the acoustical and structural performances. The effect of ambient noise on the performance was also studied and reported. This COMSOL model wasis further used to investigate the effects of shape, size and material parameters on the performance and improvement in the acoustic transmission and noise isolation. The frequency response of the system was also investigated for resonance and performance in relation to auscultation of cardio, lung and other sounds. Through this research paper the researchers share the initial findings for the development of acoustical and multiphysics design aspects of the stethoscope. The ultimate objective is to leverage the improvement in the acoustics of the stethoscope for use in Telehealthcare.

1. Acoustical Design of Digital Stethoscope
for Improved Performance
Dr Raj C Thiagarajan1, Dr Prema Sankaran2, Dr Abdul Hafeez Baig3,
Er Kodeeswari Elangovan1, Dr Raj Gururajan3
1ATOA
Scientific Technologies Pvt Ltd , Bangalore, India.
2RMK Engineering College, Department of Management, Chennai, India.
3University of Southern Queensland, Toowoomba, Queensland, 4350, Australia.
ATOA Scientific Technologies
Multiphysics CAE for Innovation TM

2. ATOA Scientific Technologies (ATOAST)
•
Engineering Simulation Solution Provider
for First Time Right Design.
•
Bridge Atom to Application to Proliferate
Simulation (Multiphysics, Multiscale &
multimaterial) for cost effective
Innovation.
•
ATOAST’s Technical Vision is Driven by
Material Unity
•
ATOAST Global with HQ’s in Bangalore
•
India’s First COMSOL Certified Consultant
•
ATOAST JYOTHI Foundation empowers our
social mission.
ATOA Scientific Technologies Multiphysics CAE for Innovation TM |www.atoastech.com |COMSOL 2012| Acoustics of DS
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3. Stethoscope
•
Stethoscopes are used for
auscultation of heart, lung and
murmurs for over two centuries.
•
New development in digital
stethoscope convert acoustical
energy into other forms
(electromagnetic, electrostatic)
and back to acoustical energy.
•
Our objective is to improve the
basic acoustics for use in
telehealth environment.
ATOA Scientific Technologies Multiphysics CAE for Innovation TM |www.atoastech.com |COMSOL 2012| Acoustics of DS
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4. Telehealthcare
• There's a huge, unmet healthcare need in India.
• Unprecedented growth in mobile communication
• Telemedicine is a good for Affordable Solution
– Low cost + Digital+ Communication
– WHO eHealth /mhealth
– Quality healthcare for all
•
Digital
healthcare
devices
•
•
•
Telecommunication
Rural/Developing
Urban/Developed
Affordable,
Quality
healthcare
ATOA Scientific Technologies Multiphysics CAE for Innovation TM |www.atoastech.com |COMSOL 2012| Acoustics of DS
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5. Acoustical Design
• Performance improvement
• Sound propagation
• Noise effects
• Material of construction
• Geometry
ATOA Scientific Technologies Multiphysics CAE for Innovation TM |www.atoastech.com |COMSOL 2012| Acoustics of DS
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6. Governing Equation
• The acoustic wave propagation
in the stethoscope is governed
by the wave propagation
equation.
• The frequency domain
pressure acoustics interface in
COMSOL was used for this
investigation.
• Sound waves in a lossless
medium are governed by the
inhomogeneous Helmholtz
equation.
1 2 p

2
 0 cs t 2
 1

p  q 
.  
 

0


Q
Where,
ρ0 in kg/m3,
refers to the density
cs in m/s
is the speed of sound,
p in (N/m2),
is the differential Pressure
Q in 1/s2
is the source
ATOA Scientific Technologies Multiphysics CAE for Innovation TM |www.atoastech.com |COMSOL 2012| Acoustics of DS
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7. DoE Design and Simulation
• Parametric CAD model and FEA mesh
• The air column inside the stethoscope,
Aluminum or stainless steel casing and
the surrounding air were modeled as
separate domains.
• The model was equipped to investigate
the effects of geometry, construction
material, and environment variables on
the acoustic performance for
optimization.
• The frequency response of the
stethoscope from 10 to 2000 Hz was
investigated.
Density
(kg/m2)
Speed of
sound
(m/s)
Aluminum
2700
6420
Brass
8480
390
Stainless Steel
7850
6100
Material
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8. Results and Discussion
• Sound Pressure
level of the air
column
• Propagation
pattern varies with
frequency
Sound Pressure at 100 Hz
• Significant for
auscultation and
signal processing.
Sound Pressure level at 1500 Hz.
ATOA Scientific Technologies Multiphysics CAE for Innovation TM |www.atoastech.com |COMSOL 2012| Acoustics of DS
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9. Results and Discussion
• Sound propagation
performance of the
stethoscope with the air
column and Al casing
• Contributes to the
efficiency of the sound
propagation
Frequency response
Sound Pressure level of the aluminum
stethoscope at 100 Hz.
Sound Pressure level of the aluminum
stethoscope at 1500 Hz.
ATOA Scientific Technologies Multiphysics CAE for Innovation TM |www.atoastech.com |COMSOL 2012| Acoustics of DS
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10. Results and Discussion
• Auscultation Pressure +
Noise Input
• Interaction effects as
function of frequency
on the transmission.
• SS vs AL
Sound Pr level at the for SS and AL Stethoscopes
Pressure and noise interaction contour plots of
stainless steel stethoscope at 100 Hz.
Pressure and noise interaction contour plots of
stainless steel stethoscope at 1500 Hz
ATOA Scientific Technologies Multiphysics CAE for Innovation TM |www.atoastech.com |COMSOL 2012| Acoustics of DS
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11. Conclusion
• Parametric COMSOL model is useful in estimating the
performance of the stethoscope.
• Geometry, Frequency, noise, material construction
performance investigated.
• Results will be used to improve the performance for use
in telehealth environment.
• Multiphysics coupling and FSI will be used in the future
for product design and finalization.
ATOA Scientific Technologies Multiphysics CAE for Innovation TM |www.atoastech.com |COMSOL 2012| Acoustics of DS
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