Abstract:

ESDU 94035 provides a computerized method of estimating the effect of the sound wave reflected from the ground surface on the measured noise signal. Ground reflection corrections are provided in the form of a difference spectrum between the measured and free-field spectra. The calculation procedure takes into account the ground impedance and air turbulence. Guidance on the required values of ground impedance and turbulence parameters is given for a range of conditions. The program may also be used to correct a measured spectrum, automatically adjusting for any discrepancy between the cancellation frequencies of the predicted and measured spectra. Such discrepancies may arise from atmospheric turbulence, errors in source location or timing errors. An allowance may be made for the characteristics of the filters used to analyse measured data. The possible ways of minimizing ground reflection effects by the suitable choice of microphone heights are discussed.

Full documentation for the programs, referred to as ESDUpac A9435 and VIEWpac M9435, is provided together with an input and output example.