User's Manual

Radical-7 Chapter 1: Technology Overview
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Patient
The generation of respiratory sounds is primarily related to turbulent respiratory airflow in
upper airways. Sound pressure waves within the airway gas and airway wall motion
contribute to the vibrations that reach the body surface and are recorded as respiratory
sounds.
Although the spectral shape of respiratory sounds varies widely from person to person, it is
often reproducible within the same person, likely reflecting the strong influence of
individual airway anatomy [2-6].
Sensor
The sensor captures respiratory sounds (and other biological sounds) much like a
microphone does. When subjected to a mechanical strain, (e.g., surface vibrations generated
during breathing), the sensor becomes electrically polarized.
The degree of polarization is proportional to the applied strain. The output of the sensor is
an electric signal that includes a sound signal that is modulated by inspiratory and
expiratory phases of the respiratory cycle.
Acquisition System
The acquisition system converts the electric signal provided by the sensor into a digital
signal. This format allows the signal to be processed by a computing device.