Equipment has been developed for the direct measurement of the attenuation of short pulses of audiofrequency sound in the open. The source consists of a 500‐cycle, one‐quarter wave pipe which is excited at intervals of about 10 sec. by an explosive mixture of acetylene and oxygen. The damped sound wave thus produced is first received by a near reference microphone and after an interval of time at a second distant microphone. Appropriate calibration and timing circuits are provided to actuate a single sweep oscilloscope as the sound pulse passes each microphone. The signal from the distant station is returned to the near station by f‐m. Both signals are recorded automatically by a solenoid operated camera. A second oscilloscope and continuous film camera provides accurate transit time records. By observing the reduction in sound intensity between the two stations and making correction for the divergence of the sound wave, the attenuation is computed. The values thus obtained are compared with those calculated from laboratory measurements under similar temperature and humidity conditions.