Publications
Nussbaumer M, Agarwal A: Stethoscope acoustics. In: Journal of Sound and Vibration, vol. 539, no. 117194, pp. 1–18, 2022. @article{NA2022,
title = {Stethoscope acoustics},
author = {M. Nussbaumer and A. Agarwal},
doi = {https://doi.org/10.1016/j.jsv.2022.117194},
year = {2022},
date = {2022-10-24},
journal = {Journal of Sound and Vibration},
volume = {539},
number = {117194},
pages = {1--18},
abstract = {For over 200 years, stethoscopes have been used to diagnose disease by listening to the sounds from the human body. However, the physics of how stethoscopes work remains poorly understood, mainly because their performance depends not only on the stethoscopes themselves, but on the coupled system that forms when the hand of a clinician presses the device against the chest of a patient. We develop an experimental setup that allows us to characterise the effect of each constituent part on the behaviour of the coupled system. By using a suitably instrumented ‘chest phantom’ we are able to quantify the response of stethoscopes in a repeatable manner and account for the effect of the phantom on the response. We provide a theoretical framework for understanding the acoustics of the coupled stethoscope system and propose a low-order lumped-element model that captures the effects of the key design choices. For example, minimising the air cavity volume inside the stethoscope maximises the response, while a stethoscope’s tubing significantly attenuates the response and introduces distorting standing-wave resonances. Using a diaphragm attenuates the response and shifts the resonances to higher frequencies. However, it also allows the air cavity volume to be minimised, which can offset the attenuation. We dispel several misconceptions, such as that the stiffness of diaphragms leads to an amplification of higher frequencies or that the dimensions of the rim and the mass of the chestpiece play no role in stethoscope performance. We hope that this paper will help to optimise the design of stethoscopes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
For over 200 years, stethoscopes have been used to diagnose disease by listening to the sounds from the human body. However, the physics of how stethoscopes work remains poorly understood, mainly because their performance depends not only on the stethoscopes themselves, but on the coupled system that forms when the hand of a clinician presses the device against the chest of a patient. We develop an experimental setup that allows us to characterise the effect of each constituent part on the behaviour of the coupled system. By using a suitably instrumented ‘chest phantom’ we are able to quantify the response of stethoscopes in a repeatable manner and account for the effect of the phantom on the response. We provide a theoretical framework for understanding the acoustics of the coupled stethoscope system and propose a low-order lumped-element model that captures the effects of the key design choices. For example, minimising the air cavity volume inside the stethoscope maximises the response, while a stethoscope’s tubing significantly attenuates the response and introduces distorting standing-wave resonances. Using a diaphragm attenuates the response and shifts the resonances to higher frequencies. However, it also allows the air cavity volume to be minimised, which can offset the attenuation. We dispel several misconceptions, such as that the stiffness of diaphragms leads to an amplification of higher frequencies or that the dimensions of the rim and the mass of the chestpiece play no role in stethoscope performance. We hope that this paper will help to optimise the design of stethoscopes. |
McDonald A, Agarwal A, Gales M J F: Detection of heart murmurs in phonocardiograms with parallel hidden semi-Markov models. Proceedings of Computing in Cardiology 2022, 2022. @proceedings{MAG22,
title = {Detection of heart murmurs in phonocardiograms with parallel hidden semi-Markov models},
author = {A. McDonald and A. Agarwal and M. J. F. Gales},
year = {2022},
date = {2022-01-20},
publisher = {Proceedings of Computing in Cardiology 2022},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
|
J. Håkansson Q X, Elemans C P H: Aerodynamics and motor control of ultrasonic vocalizations for social communication in mice and rats. In: BMC Biology, vol. 20, no. 3, pp. 1–15, 2022. @article{hakansson2022,
title = {Aerodynamics and motor control of ultrasonic vocalizations for social communication in mice and rats},
author = {J. Håkansson, W. Jiang, Q. Xue, X.Zheng, M. Ding, A. Agarwal and C. P. H. Elemans},
doi = {https://doi.org/10.1186/s12915-021-01185-z},
year = {2022},
date = {2022-01-07},
journal = {BMC Biology},
volume = {20},
number = {3},
pages = {1--15},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
McDonald A, Agarwal A, Marr C: Machine intelligence for the detection of equine heart murmurs. In: Equine Veterinary Journal, vol. 54, pp. 15–16, 2022. @article{MAM22,
title = {Machine intelligence for the detection of equine heart murmurs},
author = {A. McDonald and A. Agarwal and C. Marr},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {Equine Veterinary Journal},
volume = {54},
pages = {15--16},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Gregory A L, Agarwal A, Lasenby J: An experimental investigation to model wheezing in lungs. In: Royal Society Open Science, vol. 8, no. 2, pp. 1–20, 2021. @article{Gregory2021,
title = {An experimental investigation to model wheezing in lungs},
author = {A. L. Gregory and A. Agarwal and J. Lasenby
},
doi = {https://doi.org/10.1098/rsos.201951},
year = {2021},
date = {2021-02-24},
journal = {Royal Society Open Science},
volume = {8},
number = {2},
pages = {1--20},
abstract = {A quarter of the world's population experience wheezing. These sounds have been used for diagnosis since the time of the Ebers Papyrus (ca 1500 BC). We know that wheezing is a result of the oscillations of the airways that make up the lung. However, the physical mechanisms for the onset of wheezing remain poorly understood, and we do not have a quantitative model to predict when wheezing occurs. We address these issues in this paper. We model the airways of the lungs by a modified Starling resistor in which airflow is driven through thin, stretched elastic tubes. By completing systematic experiments, we find a generalized ‘tube law’ that describes how the cross-sectional area of the tubes change in response to the transmural pressure difference across them. We find the necessary conditions for the onset of oscillations that represent wheezing and propose a flutter-like instability model for it about a heavily deformed state of the tube. Our findings allow for a predictive tool for wheezing in lungs, which could lead to better diagnosis and treatment of lung diseases.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A quarter of the world's population experience wheezing. These sounds have been used for diagnosis since the time of the Ebers Papyrus (ca 1500 BC). We know that wheezing is a result of the oscillations of the airways that make up the lung. However, the physical mechanisms for the onset of wheezing remain poorly understood, and we do not have a quantitative model to predict when wheezing occurs. We address these issues in this paper. We model the airways of the lungs by a modified Starling resistor in which airflow is driven through thin, stretched elastic tubes. By completing systematic experiments, we find a generalized ‘tube law’ that describes how the cross-sectional area of the tubes change in response to the transmural pressure difference across them. We find the necessary conditions for the onset of oscillations that represent wheezing and propose a flutter-like instability model for it about a heavily deformed state of the tube. Our findings allow for a predictive tool for wheezing in lungs, which could lead to better diagnosis and treatment of lung diseases. |
