Development of New Measuring Method of thin film thickness using Sound Frequency

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When the sound wave is radiated upon a thin film mounted on a rigid box containing a air-layr, the thin film and air-layr resonate under a certain frequency. The resonant frequency depends upon the thickness of the film. The resonant frequency varies almost linearly with the thickness of the film. The experiments were conducted under various conditions in order to find important factors affecting on the frequency. The experiments for the plate to measure its thickness were also conducted. Following conclusions were introduced.** The position of the sound source upon the film does not give an affect on the resonant frequency.** From the experiments not only for the polyethylene, vinyl chloride, acryle and nylon, it was clear that the thickness of the thin film can be measured from the resonant frequency.** Similar resonant frequencies were obtained in both experiments, one is to use wide range white noise and another one is to sweep the pure tone.** This measuring method is not applicable for the hard materials such as a hard plate because the hard plate does not resonate by the sound wave from a speaker.