Photoacoustic spectroscopy of biomedical gas sensing: Adaptive filtering as calibration

New severe requirements of measurements of anaesthetic gaseous components oblige to be accurate in evaluating concentrations in hospital facilities, especially in surgical pavilions. Exposure to anaesthetic gases in the health sector, whether in the operating room, recovery room, or in the context of outpatient clinics, may entail a health risk for the personnel exposed. Although health care workers are exposed to much lower anaesthetic concentrations than the patients, this exposure often extends over many years. Personnel often indicates fatigue and headaches, especially when occupational hygiene conditions are inadequate. The decisive factors as concerns, the adverse health effects of exposure to anaesthetic gases, are mainly the type of gases used, the length of exposure, and the gas concentrations. This paper aims to describe an alternative procedure of calibrating a photoacoustic instrumentation by extracting signal from acoustic sensors, that are microphones. The alternative procedure is based upon Frost beamformer algorithm preceded by a smoothing thanks to Savitsky-Golay method. A comparison has been performed using the same alternative procedure but by substituting Frost beamformer with a notch filter.