Sound transmission in the thorax

The use of an intracardiac sound source to determine transfer functions and propagation paths and modes for the thorax using digitial data reduction techniques is discussed. It is important to know the sound transmission characteristics of the thorax for diagnostic purposes. Studies made using naturally occurring heart sounds have not satisfactorily defined either the origin or the transmission modes and paths for the signals. An intracardiac sound source inserted by standard cardiovascular catherization techniques [“Artificial Sound Production in the Cardiovascular System,” H. C. Merchant et al., J. Assoc. Advan. Med. Inst. 7, No. 4 (Sept. 1973)] was used as the sound source. The sound source and external receiver were located in three dimensions using x-ray techniques [“Three Dimensional Location Using Planar X-ray Systems,” R. D. Golden et al., J. Assoc. Advan. Med. Inst. 6, No. 3 (May 1972)]. Preliminary experiments were performed using experimental animals. The analog data were digitated and reduced on a digital computer using correlation and spectrum analysis techniques.