A semicircular array, 30 ft in diameter, of 41 five‐inch loudspeakers has been built in the Harvard anechoic chamber to provide a two‐dimensional isotropic noise background. A separate gas‐tube noise generator powers each speaker. Signals can be superposed on the noise applied to any speaker. With this array it is possible to study methods of detecting and locating signals in such a background. Included in the instrumentation is circuitry for the measurement of the signal‐to‐fluctuation‐noise ratio at the detector output. Preliminary experiments using a two‐element array and a square‐law or correlation detector have been carried out. The measured patterns and signal‐to‐noise ratios are in good agreement with theory.