This study of jungle acoustics was carried out during the wet season in Panama. Within a jungle the temp. and wind velocity gradients are so small that the sound refraction they produce may be neglected for all practical purposes. Humidity increases the transmission loss at high frequencies and field measurements of the loss agree with laboratory values reported by others. Terrain loss in the jungle was found to increase linearly with distance. The terrain loss coeffs., (in db per foot), were measured for various types of jungle and were found to be a function of frequency and of the density of the terrain. The level of the ambient noise in the wet. season jungle is very low especially for the quiet periods between animal calls. At night the low frequencies decrease as the light breezes cease and the high frequencies increase as the insects begin their nocturnal chorus. The probable error of judgment in the localization of a sound source is large, of the order of 20[degree]. This error is greatest for sound sources either in front or back and least if the sound source is in the direction of the interaural axis. For the range investigated (300-600 ft.) the error decreases as the sound source moves further away.