Auscultation in high‐noise environments using hybrid electromechanical and ultrasound‐Doppler techniques

Medical evacuation of battlefield casualties or traffic accident victims by air typically takes place in very noisy environments. Auscultation of patients, e.g., to support chest intubation or to detect a pneumothorax, is therefore difficult or impossible to perform. A conventional acoustic stethoscope will not function very well in background noise levels beyond 80 dB. Electronic stethoscopes, in combination with mechanical impedance‐matched transducer designs, can extend this range to about 90 dB, but this is not enough for helicopter noise levels that can reach 110 dB. The use of an ultrasound transmitter and receiver, however, provides an essentially noise‐free auscultation channel since transportation vehicles do not produce acoustic energy at ultrasound carrier frequencies of 2–3 MHz. Clean and noise‐free heart and breath sounds have been obtained in broadband noise fields of intensities as high as 120 dB. A hybrid stethoscope has been developed that allows auscultation by ultrasound‐Doppler as well...