The echolocation signals used by two species of bats,Chilonycteris rubiginosaandEptesicus fuscus, were recorded with four microphones in an array about the bat's head. The bats were trained to broadcast their sounds at a small. Stationary target, and the microphones were arranged in the horizontal plane at angles of 0°, 22.5°, 43°, and 90° with respect to the direction in which the bat pointed its head. The signals produced by both species were directional, with most of the energy projected straight ahead. The sound pressures recorded 22.5° away from the main axis of the broadcasts were about half as great as those recorded from directly in front of each bat.Chilonycterisappears to use a slightly more directional beam thanEptesicus.