"Buzz-saw" noise: a comparison of modal measurements with an improved prediction method

McAlpine, A., Fisher, M.J. and Tester, B.J. (2007) "Buzz-saw" noise: a comparison of modal measurements with an improved prediction method. Journal of Sound and Vibration, 306 (3-5), 419-443. (doi:10.1016/j.jsv.2007.04.053).

Abstract

“Buzz-saw” noise is radiated from a turbofan inlet duct when the fan tip speed is supersonic. In a recent article the effect of an acoustic liner on buzz-saw noise has been examined. Spectral measurements in a rigid and an acoustically lined inlet duct have been compared. Also these measurements have been utilized to assess a buzz-saw noise prediction method. The prediction method is based on a one-dimensional nonlinear propagation model. Sound absorption by an acoustic lining can be included in the model. In this article, the buzz-saw noise prediction method is improved by the inclusion in the modelling of the effect of a boundary layer on absorption of sound in a lined duct. Also, modal measurements from a circumferential microphone array have been examined. These show that the principal source of buzz-saw noise is not always the rotor-alone pressure field. Non-rotor-alone scattered tones can be a significant source of buzz-saw noise at low supersonic fan speeds. The numerical simulations, which only predict the rotor-alone tones, have been re-evaluated in light of these new modal measurements.

This record has no associated files available for download.

Contributors

Author: A. McAlpine

Download statistics