This chapter described the development of a medical instrument used to measure changes
in the distribution and density of fluid within the respiratory system. The instrument used
principles of sound emitting, acquisition, and processing to obtain the impulse response
of an unknown system through adaptive filtering. Parameters such as sound propagation
delay and the system transfer function can be extracted from the impulse response. The
instrument is also capable of attaching to both phantom and human chests due to a fully
adjustable harness that holds an array of electronic stethoscopes.