An apparatus for measuring at least one parameter associated with a fluid flowing within a
pipe comprises an optical
measurement device and a
signal processor. The optical
measurement device provides output signals indicative of unsteady pressures within the fluid at two or more axial locations along the
pipe in response to light reflected from an outer surface of the
pipe. The
signal processor provides an output
signal indicative of at least one parameter associated with the fluid in response to the output signals. The optical
measurement device may include, for example, an electronic
speckle pattern interferometer, a Fabry-Perot device, and / or a
laser vibrometer. The at least one parameter may include at least one of: density of the fluid, volumetric flow rate of the fluid,
mass flow rate of the fluid, composition of the fluid, entrained air in the fluid, consistency of the fluid, size of particles in the fluid, and health of a device causing the unsteady pressures to be generated in the pipe.