The paper gives a brief description of the principles and the uncertainty of the acousticcalibration methods that today are applied by National Metrology Institutes andcalibration service centers. Even if some of the calibration principles have been appliedover more than half a century, the methods and the instrumentation are still being refinedin order to minimize their uncertainty, to extend their frequency ranges, to include extraparameters and to speed up slow processes. In addition to the traditional methods formicrophone sensitivity and frequency response calibration, new development areas, like forexample wind power, has created needs for low-frequency and infra-sound calibration, downto 0.1 Hz. Other high-tech areas have lead to the development of methods for phaseresponse comparison calibration of microphones for large arrays, for sound intensitymeasurement and for verification of dynamic linearity of microphones at very high soundpressure levels, up to about 174 dB that corresponds to 10 kPa.

A hybrid differential transformation / finite difference scheme is used to analyze the complex nonlinear behavior of an electrostatically-actuated micro cantilever beam which high aspect ratios (length/width). The validity of the proposed method is confirmed by comparing the numerical results obtained for the tip displacement and pull-in voltage of the cantilever beam with the analytical and experimental results presented in the literature. The hybrid scheme is then applied to analyze both the steady-state and the dynamic deflection behavior of the cantilever beam as a function of the applied voltage. Overall, the results confirm that the hybrid method provides an accurate and computationally-efficient means of analyzing the complex nonlinear behavior of both the current micro cantilever beam system and other micro-scale electrostatically-actuated structures.