Abstract
We propose a method to improve the sensitivity of a micro ultrasonic wave sensor using Helmholtz resonance. By this method, we improve the sensitivity by 23.8 [dB], getting 15.5 times greater amplitude of the vibration of the cantilever, which was used as the sensor, compared with the normal cantilever. We also made two more experiments to measure how the sensitivity changed according to the relationship between the resonance frequency of the Helmholtz cabity and the natural frequency of the cantilever. As a result, the sensitivity was the highest when these two frequencies were the same. The peak of resonance was not so sharp that the sensitivity was more than the half of its maximum when the resonance frequency of the Helmholtz cabity was in the range of 92.6 - 108.9% of the natural frequency of the cantilever. Moreover, there was also a peak at the resonance frequency on the frequency properly of the sensor, even if there was a small gap between the two frequencies.
