Patent ID: 8806734

Claim:
A method of producing an ultrasonic flowmeter comprising the steps of: fabricating a tube made of a sound absorbing material made of a polymer filled with attenuative particles, the polymer is either an epoxy, nylon, PTFE or PEEK, the particles are either metal, metal oxide, glass microspheres or rubber having a mesh size less or equal to the acoustic wavelength, the tube has a length L and a diameter opening D such that under volume flow conditions where Q>0.2 liters/hour, the tube dimensions L/D^2 are greater than 1385/meters when C>1400 m/s, where C is a speed of sound in the fluid; machining in the tube a channel having a constant inner diameter through which fluid flows; and attaching the tube to the ultrasonic flowmeter so that essentially all non-fluid paths of sound produced by transducers of the flowmeter are absorbed by the tube.