Short-time Fourier and wavelet transform analysis of respiration signal obtained by thermal imaging

Respiration rate is a critical sign of a person's wellbeing. The respiration rate of an adult subject was measured for eight minutes using a thermal imaging technique. A suitable algorithm was used to locate and track the respiration region of interest centred on the tip of the nose. The effectiveness of short time Fourier transform (STFT) and continuous wavelet transform (CWT) to determine respiration rate variations over time was investigated. The study indicated that both STFT and CWT can indicate respiration rate time variations, but CWT was more sensitive in detecting the transient changes in respiration signal.