Wristwatch with piezoelectric buzzer

In a wristwatch having a watch case and a case back releasably secured to said watch case, said case back having a lower surface defining an interior side and an opposite exterior side, the exterior side of the lower surface of said case back contacting the wrist of a wearer when said wristwatch is worn, the improvement comprising a piezoelectric element coupled to the interior side of the lower surface of said case back inside said watch case so that the lower surface of said case back acts as a vibration plate means for said piezoelectric element, said case back having a natural resonance frequency when said wristwatch is not worn and an apparent resonance frequency when said wristwatch is worn and in contact with the skin of a wearer, driver means for producing a driving signal for driving said piezoelectric element, the frequency of said driving signal being proximate to the apparent resonance frequency of said case back when said wristwatch is worn, the natural resonance frequency of said case back when said wristwatch is not worn being set to between about 5.5 kHz and 7.0 kHz, said case back being formed so that the apparent resonance frequency of said case back is about 4 kHz whereby the volume of sound from said piezoelectric element and said case back when driven by said driving signal does not substantially vary when said wristwatch is worn and when not worn.