Propeller noise is generally not as loud or as disturbing as jet noise, but is more difficult to reduce. We are, therefore, directing our efforts mainly to the field of jet noise, where useful contributions to a solution seem more probable.

The Ministry of Supply assists fundamental research into jet noise at the College of Aeronautics and some of our universities, and has contracts with leading aircraft companies to devise methods of noise suppression. The most successful method so far developed is the corrugated jet nozzle produced by Rolls Royce Limited under contract with the Ministry of Supply. These nozzles have been fitted to the Comet IV.