Physical modeling is a technique wherein sensorimotor mechanisms believed to underlie animal behavior are mimicked using functionally analogous transducers and electromechanical circuitry. Because physical models inhabit the same environment as animals, they allow biologists to examine more realistic environmental interactions. In turn, physical modeling can enable engineers to discover the general principles underlying robust, adaptive sensorimotor control of robots. Two acoustic localization mechanisms are being physically modeled: cricket phonotaxis and echolocation by constant frequency emitting bats. (1) The function of the cricket trachea was modeled by connecting the output of two miniature microphones to a circuit measuring the relative intensity and binaural phase shift of a received call. Using only tracheal phase cancellation and latency comparison, a robot bearing this sensor obtains directional information enabling it to approach only those sounds with the right (frequency and envelope) structure. (2) An artificial echolocation system was built using a continuous, pure-tone-emitting transducer and a pair of receivers mounted on the pan/tilt head of a robot. Directional cues contained in echoes reflected from moving targets---interaural intensity disparities and temporal differences in the echo modulating waveforms---are used to orient the robot toward these targets.