Abstract: The invention concerns a flowmeter including a pipe (2) and two ultrasound transducers mounted facing one another and oriented in a measurement direction at a non-zero angle less than 90° to a longitudinal axis of the pipe and including a casing (8) including a main receptacle (9) mounted on said pipe, a first sleeve (10) and a second sleeve (11) extending in a direction orthogonal to the longitudinal axis of said pipe, projecting from a bottom of the main receptacle (9) and on either side of said pipe, each sleeve (10, 11) being configured so as to cover said first or second ultrasound transducer at least partly so as to delimit a receiving internal volume, the main internal volume of the main receptacle being in communication with said receiving internal volumes of said first and second ultrasound transducers. The invention also concerns a method of assembling a flowmeter of this kind.