Cross spectra between temperature and pressure in a constant area duct downstream of a hydrogen fueled combustor

It was shown in a recent paper [J. H. Miles and E. A. Krejsa, J. Acoust. Soc. Am. 72, 2008–2019 (1982)] that knowledge of pressure‐temperature auto spectra and cross spectra could be used in a model for sound propagation in a variable duct having acoustic and convected entropy fluctuations. The present exploratory study investigates the measurement of pressure‐temperature cross spectra and coherence and temperature cross spectra and coherence at well separated points in a combustion rig. Data obtained near the inlet and the exit of a 6.44‐m‐long duct attached to a J‐47 combustor fueled with hydrogen are presented.