Abstract: A vibrating transducer for detecting the resonant frequency of a vibrating diaphragm and using that frequency to determine the pressure or density of a fluid contacting the diaphragm. The device includes a container having a diaphragm separating the cavity in the container into two chambers with the diaphragm preventing flow communication between the two chambers. A first fluid inlet in flow communication with the first chamber introduces fluid to the first chamber with that first chamber having an acoustic compliance less than the mechanical compliance of the diaphragm. The second fluid input is in flow communication with the second chamber and introduces fluid into the second chamber. By controlling the acoustic compliance of the chamber with respect to the diaphragm accurate measurements of the density or pressure of the fluid can be obtained.