E. J. Richards, J. L. Willis, and D. J. M. Williams 299 
REFERENCES 
1. M.K. Bull, "Instrumentation for and Preliminary Measurements of Space—Time Correlations and 
Convection Velocities of the Pressure Field of a Turbulent Boundary Layer,” AASU Report 149. 
. J. L. Willis and M.K. Bull, "Progress Report on Flow Noise Investigation,” AASU Report 182, 
. W. W. Willmarth, "Statistical Properties of the Pressure Field in a Turbulent Boundary Layer,” 
WADC Conf. on Acoust. Fatigue (October, 1959), 
4, D. J.M. Williams, "Measurements of the Surface Pressure Fluctuations in a Turbulent Boundary Layer 
in Air at Supersonic Speeds,” AASU Report 162. 
5. M. Judd and J.P. Jones, "Surface Pressure Fluctuation Correlation Measurements on a 70° Delta 
Wing," ACR. 22428 (December, 1960). 
6. D.J.M. Williams and I. J. Sharland, "An Experiment on the Noise from a Flat Plate Aerofoil in a 
7 
wn 
Turbulent Subsonic Jet," Southampton Univ., Internal Note. 
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171. 
8. B.L. Clarkson and R.D. Ford, "Experimental Study of the Random Vibrations of an Aircraft Structure 
Excited by Jet Noise," AASU Report 128. 
9. D. J. Mead, "The Damping, Stiffness and Fatigue Properties of Joints and Configurations Representative 
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10, R. Mangiarotty, M. Sc. Thesis, Univ. of Southampton (1961). 
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Supported Ends," Proc. Roy. Soc., A 197, 238-256 (1949), 
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DISCUSSION 
MR. A. KENDRICK asked the lecturer whether he had reconciled his calcu- 
lation of total noise power with results obtained by the methods of N. Curle and 
O.M. Phillips. 
PROFESSOR RICHARDS: Phillips has calculated the noise radiated by 
relating it dimensionally to the skin friction at each point and, therefore, to the 
drag coefficient of the plate. It was, naturally, necessary to assume some re- 
lationship between the fluctuating pressure field and the local skin friction, and 
this he did using the known theory of flowing turbulence. The advantage of our 
calculations lies in the use of measured fluctuations and correlation areas and, 
therefore, eliminates any uncertainties (and there are plenty) in using isotropic 
homogeneous -turbulence theories in a shear region. Inpractice and as far as my 
recollection goes, Phillips's results also give noise levels which are some 30 
db lower than in practice, a result in agreement with ours. Needless to say, 
Phillips does not go on to study the effects of roughness nor of panel oscillations. 
