An apparatus for measuring a parameter of a fluid passing through a pipe comprises a spatial array of pressure sensors disposed at different axial locations along the pipe between a sleeve within the pipe and an inside surface of the pipe. Each of the pressure sensors provides a pressure signal indicative of unsteady pressure within the pipe at a corresponding axial location of the pipe. A signal processor is configured to receive the pressure signals from each of the pressure sensors, and determine the parameter of the fluid using the pressure signals from the pressure sensors. The sleeve and the sensors may be disposed within a pipe spool piece having flanges disposed on opposing ends. The pipe may be formed from a material relatively more rigid than the sleeve, and the sensors may be compressed between the pipe and the sleeve. The sleeve may have grooves formed therein for receiving the sensors, and each sensor may be formed from a piezocable wrapped around the sleeve.