When an electric field is applied to a piezo-electric film it deforms (see Figure 17). We will use this property to make a flat piezo-film speaker. For efficency, a large piece of piezo material is used. The piezo film speaker measures 3 inches by 6 inches.
When using this material as a speaker, it is necessary to provide a high voltage audio signal. This is accomplished by feeding a standard audio signal through a step-up transformer.