Our two ears

Before the 1900s people rarely gave a second thought about our two ears, the appendages necessary to experience the world in three dimensions. That all changed when Clément Ader demonstrated the first two-channel audio system in Paris. On that day in 1881, Ader setup a pair of telephones on the Paris Opera stage and connected them to another set in a suite of rooms at the Paris Electrical Exhibition, where listeners could hear a live transmission of performances through receivers for each ear. Scientific American reported:

"Every one who has been fortunate enough to hear the telephones at the Palais de l'Industrie has remarked that, in listening with both ears at the two telephones, the sound takes a special character of relief and localization which a single receiver cannot produce.... This phenomenon is very curious, it approximates to the theory of binauricular audition, and has never been applied, we believe, before to produce this remarkable illusion to which may almost be given the name of auditive perspective."

No one had experienced stereo playback before and it would take another 53 years before Allen Blumlein would change all that. The year was 1931 and Blumlein was unhappy with talking motion pictures. The voices of actors walking across the big screen did not move with them. Instead, all the audio came from the center of the screen through a single monaural loudspeaker. Within 4 years Blumlein had not only solved the problem with what we would eventually call stereo, he also figured out how to place stereo microphones and how to cut stereo tracks into monaural records. Because of Blumlein's invention, and the work of others like Ader and Bell Laboratory's Harvey Fletcher, our world more closely resembles the three dimensions we've lived with because of our two ears since the dawn of mankind. If you're interested in finding out more how modern speaker pairs create 3D sound as well as a few tips on improving their abilities to do so, watch my latest video here.