Study of Intelligibility Improvement with Out-of-Phase Connections of Headphones
D. Greenberg, H. O. Benecke · The Journal of the Acoustical Society of America · 1961
Previous work on the effect of interaural phase relations on the masking of speech by white noise, suggested the possibility of improving communication in ambient noise by simply reversing the connections of one earphone of the headset to produce out-of-phase reception. A series of intelligibility tests was conducted at the U. S. Naval Air Development Center, Johnsville, Pennsylvania, in 1949 to determine whether improvement could be obtained under conditions simulating those encountered in naval aircraft. Headphones in use then were almost entirely connected in-phase. The results of intelligibility tests, performed with listeners subjected to 119 db of simulated reciprocating-engine aircraft noise, showed that for low and intermediate signal levels, the out-of-phase scores averaged only about five percentage points higher than in-phase scores; for high signal levels, the out-of-phase scores were about five percentage points less. The overall results did not indicate any significant advantage for the out-of-phase connection for communications in naval aircraft.