Estimation of Aeroplane Noise Level: Some Empirical Laws with an Account of the Present Experiments on which they are Based

AIRSCREW noise, engine noise and aerodynamic noise combine to produce the high noise level of an aeroplane. Much information has been obtained experimentally concerning these noises and the loudness level they produce when occurring together. The possibility of applying this information, to predict the noise level of projected aircraft, recently promoted a further review of the data, and some new expressions were framed, which, together with other older and well‐tried formulæ, linked together tolerably well the results of the several experiments. These empirical laws, which have proved of considerable value in several problems relating to the improvement of aeroplane noise, are now put forward. At the same time the basic experiments are outlined so that those who may use the expressions will be aware of possible limitations.