Transducer

1. An inertial force transducer having an operative frequency range and comprising

a resonant element having a frequency distribution of modes in the operative frequency range of the transducer, the resonant element being a piezoelectric device and comprising

a layer of piezoelectric material and

a substrate layer on the layer of piezoelectric material, and

coupling means for mounting the resonant element to a site to which force is to be applied,

characterised in that the substrate layer has a region extending beyond the piezoelectric layer, with the coupling means mounted to the extended region whereby the low frequency performance of the transducer is extended.

2. A force transducer accord to claim 1 , wherein the parameters of the extended region are selected to enhance the modality of the resonant element.

3. A force transducer element is generally rectangular or beam-like and wherein the extended region of the substrate layer is one end of the resonant element.

4. A force transducer according to any preceding claim, wherein the bending stiffness of the coupling means is greater than the bending stiffness of the extended region.

5. A force transducer according to any preceding claim, wherein the substrate layer and the coupling means are coupled together with a rigid connection.

6. A force transducer according to any preceding claim, wherein the resonant element is a piezoelectric bimorph.

7. A force transducer according to any preceding claim, wherein the substrate layer is metallic.

8. A force transducer according to any preceding claim, comprising a plurality of resonant elements.

9. A loudspeaker comprising a force transducer as claimed in any preceding claim.

10. An electronic device comprising a loudspeaker as claimed in claim 9 .

11. A mobile telephone or cell-phone comprising a loudspeaker as claimed in claim 10 .