This thesis contains a detailed report of the design, construction and testing of the prototype of a new assistive listening device. The project objective was to design a device that would use a sound localizing algorithm based on human auditory function to determine the position of a target sound source, and would then automatically steer a highly directional microphone to that position. Preferentially amplifying only the intended sound source provides a much cleaner signal for the user, and improves speech intelligibility. Such a device would be useful in controlled environments such as in the classroom, at a business meeting, or situation where there was orderly conversation with only one speaker at a time. The completed device consists of an array of three omnidirectional microphones, a small directional microphone mounted on a motorized rotating platform, and a digital signal processing (DSP) board. Sound samples collected from the omnidirectional microphones are stored on the DSP board, and are analyzed to determine the position of any sound sources present. If a source is identified, the directional microphone is steered to point in the direction of the source. The directional microphone has a range of travel of 240 degrees, through which it can rotate in under one second, and settle on the chosen location with an error of less than five degrees. The performance of the device as a whole was tested in an anechoic environment. Results showed that the device could localize voice, sinusoidal, and pulsed signals with average errors over a variety of test configurations ranging from approximately three to six degrees.