A sensor comprises two identical vibrating members operating with a common working frequency and joined to each other by a mechanical decoupling device. The device comprises a frame and two connecting bridges each supporting one member. The frame comprises a succession of mass portions and thinned portions so that the frequency of one mode of structural resonance of the frame is substantially equal to the common working frequency, and each connecting bridge is disposed in a node of vibration of the frame at the common working frequency. Thus, the vibrations of the two vibrating members are decoupled from each other.