A frequency-domain representation of the Burgers equation reveals that the cross-spectrum between the pressure and pressure-squared waveforms can be used to calculate nonlinear frequency-domain effects of finite-amplitude sound propagation. The normalized version of the quadspectrum, Q/S, was introduced by Morfey and Howell and has since been used to point to the nonlinear transfer of energy between frequencies, in particular gaining use in the domain of high-amplitude jet noise propagation. However, one question that remained was that of the interpretation: The physical meaning of the amplitude of Q/S was unclear. Recent analytical work has recast Q/S and the normalized version of the cospectrum, C/S, as a way to estimate sound pressure level and phase changes due to nonlinearity with a single-point measurement. This paper uses various measurements within a plane-wave tube to verify the physical significance of the amplitude and phase changes predicted by Q/S and C/S. Experiments involving sinusoids and band-passed Gaussian noise at various amplitudes show the validity of the single-point measurement to measure the strength of nonlinear effects in both amplitude and phase.
|Journal||Proceedings of Meetings on Acoustics|
|Publication status||Published - 2018|
|Event||21st International Symposium on Nonlinear Acoustics, ISNA 2018 - Santa Fe, United States|
Duration: 2018 Jul 9 → 2018 Jul 13
Bibliographical noteFunding Information:
The authors acknowledge Jared Oliphant for his help in conducting measurements. B.O. Reichman was funded through an appointment to the Student Research Participation Program at the U.S. Air Force Research Laboratory, 711th Human Performance Wing, Human Effectiveness Directorate, Warfighter Interface Division, Battlespace Acoustics Branch administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and USAFRL.
© 2018 Acoustical Society of America.
All Science Journal Classification (ASJC) codes
- Acoustics and Ultrasonics