This study describes the physical foundations of biomedical engineering and bioinstrumentation in the context of their application to actual instruments. Extensive coverage of sound engineering derivations illustrates underlying principles of clinical instruments, while descriptions and classifications of clinical instruments serve to reduce confusion over the multitude of equipment currently in use. Detailed coverage of transducers and beam patterns is provided, which is essential for an understanding of instrument characteristics. Other topics discussed include the Doppler principle, examined in light of the increasing clinical importance of Doppler flowmeters and imagers, biological tissue types and ultrasonic tissue values based on actual experimental situations such as phased instruments, additional medical uses of ultrasound and safety.