Case study evaluation of the Rayleigh integral method

The Rayleigh integral is based on the assumption that the vibrating surface is flat and part of an infinite rigid baffle. Though approximate, the Rayleigh integral can evaluate the sound power radiated by a vibrating surface in a fraction of the time required by the boundary element method. Three case studies were conducted to evaluate the reliability of the Rayleigh integral. Specifically, the Rayleigh integral was used to predict the sound power from a wheel‐rail structure, a gearbox, and an engine. In each case, Rayleigh integral results were compared with boundary element results. The results indicated that sound power compared well with that obtained using the boundary element method. The differences were less than 5 dB except at low frequencies. However, the Rayleigh integral did not accurately predict the sound pressures at field points. The results suggested that the Rayleigh integral could be used in place of the more time intensive boundary element method for sound power calculations.