Notes on Quartz Plates, Air Gap Effect, and Audio-Frequency Generation

Experiments on the frequency of piezo-electric elements are described with special reference to the effect due to supersonic sound waves generated in the air gap of the holder and due to its capacity. It is shown that a mechanical load on the crystal increases its thickness frequency and that an air gap has a similar effect. The velocity of the supersonic sound waves is about the same as for ordinary sound waves. The value found is 338.68 meters per second at 24.5C deg. An appropriate air gap gives even more high-frequency output than a mechanically-loaded crystal and procures a steady frequency operation. Two sputtered piezo-electric elements can produce a beat frequency which is correct within a few parts in 100,000. A method is shown by means of which a low-frequency standard can be obtained by harmonic division of a high frequency due to piezo-electric element.