| Summary |
A new method is proposed by authors to measure membrane stresses in two different directions separately, where instead of measuring the membrane stresses directly, the natural frequencies of the membrane within fixed rectangular region resonated by sweep external excitation induced by sound is utilized. The new method makes use of the resonance phenomena of the membrane which is induced by sound excitation given through audio speaker, where the effect of the added mass of surrounding air can not be ignored for high accuracy measurement, and added mass of air was theoretically evaluated by using an equivalent circular plate. In this paper, the white noise which has the frequency fields of 0 to 500Hz is used as the external excitation instead of sweep excitation, because it has possibility that response amplitude depends on speed and time of sweep. In the verification experiment, the boundary of vibration is kept by adding the weight, and the good accuracy is obtained. It is clearly shown that the white noise excitation is quite effective to obtain the resonance frequency of the membrane and suitable for the measurement equipment of membrane stress. Moreover, the process of the divice improvement toward high accuracy and the result of experimental test carried out are presented.
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