Air control tower operators listened to test transmissions, consisting of speech intelligibility tests couched in airplane‐tower phraseology, over four channels. Part of the time the messages of two channels overlapped each other and the degree of overlap was systematically varied. The task was to respond to all messages.The results showed a decrement in performance related directly to the amount of overlap, the leading message being understood better (unless it was considerably lower in intensity). For those parts of the message which had low informational content, the messages of the overlapping channel increased the total assimilated information per unit time above the total assimilated in the absence of the competing channel messages.