Operator's Manual

Radical-7 Chapter 1: Technology Overview
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Signal
Processing
Envelope
Detection
RRa Estimation
Digital signal to
respiratory
measurement
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.