Abstract: A timepiece includes a casing having a casing interior having a viewer's side provided with a viewing opening, a base side provided with a sound aperture, and an annular surface surrounding the sound aperture. A membrane extending over the sound aperture closes the base side of the casing interior, the membrane having a circumferential region in sealed connection with the annular surface. A tensioning device maintains the membrane at a desired tension in the radial direction. A vibration generator arranged in the casing interior produces a sound whose frequency can be adjusted by adjusting the tension of the membrane.