| 摘要 |
<p>The device and procedure for breathing detection solves the problem of implementing a system for breathing detecting which features fast responsiveness, resistance to noise from the environment and self- adaptability to breathing with various dynamics or power. The system consists of classical audio earphones (5, 6,6') to which two measurement (4) and two reference (3) condenser microphones are attached, which are further via a pre-amplifying system linked to the PC where the digital processing of signals is performed. The measured quantities are first recalculated to average power of windows of 256 samples, then the surrounding noise is eliminated by deducting the average strength of reference signals from the average strength of the measurement signals. Subsequently a threshold is defined which represents the individual exhalation, which is determined by a function which defines the threshold in such a way that it adjusts it to the maximum value of the size of the processed breathing signal. This is then retained for the period of one half of the average breathing period and then reduced linearly with time according to a factor, which is reverse proportional to the average breathing period. In determining the individual exhalation (when the signal hence reaches the triggering threshold) it is necessary to apply a hysteresis function or tolerance range in the size of 5 % of the complete dynamic range, which discourages multiple triggering that may occur due to the high-frequency signal activity (hence when the magnitude would several times exceed the triggering threshold due to its high-frequency activity).</p> |
