Introduction

The invention consists of a timbre (sound source) realised by means of a two-component metallic and piezoelectric element capable of changing its fundamental frequency by means of a switch between an open circuit condition and a short circuit condition applied to the piezoelectric element. Methods are provided for calculating the relative thicknesses of the substrate and the piezoelectric part, as well as the length of the timbre that, once the constituent materials are fixed, allow the pitch change to be achieved.

Technical features

The present invention (TRL 2) allows, through a simple mechanical switch between an open circuit and a short circuit condition on a piezoelectric element, to change the fundamental frequency of the stamp, thus having at least two tones available for each stamp inside the watch case. This allows you to create more elaborate ringtones for the same number of sound sources used.
The stamp consists of a metal substrate on which two sheets of piezoelectric material are deposited. The two piezoelectric foils are polarized, and the surface in contact with the substrate is short-circuited at the same time.
By applying a different condition to the electrical boundary to the surfaces exposed to the lamia piezo, the equivalent stiffness of the composite is modified, thus modifying its dynamic response and consequently its fundamental frequency.

Possible Applications

• Luxury watch industry.

Advantages

• It allows through a simple mechanical switch to obtain (at least) two distinct notes from a single sound source.