Optically excited vibratile transducer

An optically-excited vibratile transducer (10) of microstructural form has a plurality of vibratile elements (11, 12) in stacked formation. End (10A) of the transducer (10) is connected via an optical fibre (13) to an optical device (14) for exciting and interrogating the stack. The other end (10B) of the stack is exposed to the influence of a plurality of variables, such as pressure and temperature, in a gaseous atmosphere. The elements (11, 12) are free to vibrate without mutual physical interference and are respectively decoupled from the influence of the variable. For example, element (11) is subjected to the influence of both pressure and temperature but vent (15) is provided adjacent element (12) to decouple the effect of pressure from element (12) leaving it subject only to the influence of temperature.