| 摘要 |
The invention concerns a fluid meter (10) comprising ultrasonic transducers (26, 28), means for attenuating parasitic ultrasonic waves, of wavelength .lambda., constituted by at least one passage (36, 38, 40) in which said waves propagate along a main direction corresponding to a longitudinal dimension (a) of said passage, said passage having a transversal dimension (b) perpendicular to (a) and much less than the wavelength .lambda. of the parasitic waves in the propagating medium, said passage comprising a plurality of consecutive passage portions (46, 48) each having a part (46) with a reduction of the transversal cross-section of the passage along the dimension (b) of the passage, the longitudinal dimension of each passage portion being substantially equal to .lambda./2.
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