We take headphones for granted, but back in the days of the World War I flying aces (Red Baron, anyone?) there were no such thing. So how did flying student and instructor communicate over the noise of the airplane’s motor?
With this contraption invented at the British flying school at Gosport, England:
… device whereby the instructor shouted into a funnel-like arrangement having a rubber tube divided by a “Y” which connected to ear pieces in the student’s helmet. This device became known as the “Gosport Tube” and most American pilots trained under the Gosport System believed to this date the communication device was the essential element of the system. Amazingly, the Gosport continued to be used in military training through World War II. Although it was better than nothing, the instructor had to shout into the speaking tube and then look up into the rear view mirror in an attempt to ascertain whether the cadet heard him.