Mr. Gresham Cookeasked the Minister of Aviation by what percentage the noise of the engines of the Comet 4 and Boeing 707 has been reduced by the suppressors fitted, as compared with engines not so fitted.
§ Mr. RipponSuppressors have reduced the noise of the Comet 4 by about four to six perceived noise decibels according to the power used, and that of the Boeing 707 by about ten perceived noise decibels. This means that the noise of the Comet is about two-thirds as loud and the noise of the Boeing 70732W about half as loud as before the fitting of the suppressors. However, the Comet 4, because of its higher rate of climb, is less noisy than the Boeing 707, as heard from the ground under the flight path.