This paper describes unsteady pressure measurements made on the mid span suction and pressure surfaces of a rotating turbine blade in a transient facility. The measurements were made at the engine representative conditions for this turbine using high spatial density surface mounted semi-conductor transducers. This high spatial density, coupled with the wide bandwidth capability of the sensors and data acquisition system, has enabled analyses of unsteady wave propagation effects (both in magnitude and phase) to be carried out. This paper significantly adds to the body of data available at engine representative conditions, particularly in terms of compressibility.

Distinctions are drawn between events which are propagating at free stream velocities and those which move at local acoustic velocities. Comparisons are made with theories which have been previously expounded, and some inconsistencies are outlined.

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