Methods for determining and analyzing cut-off frequency of photoacoustic signal

The paper presents the basic definitions of characteristic cut-off frequency and various methods for determining and analyzing these values of photoacoustic signals. Also, the work will check the accuracy of the methods used. The cut-off frequency represents the frequency value on the amplitude characteristic at which the gain drops by 3 dB in relation to the nominal gain (observed in a logarithmic scale). To be able to make an analogy between low-pass RC filters and the photoacoustic signal, it is necessary to determine the values of the cut-off frequencies and their further comparison with the thickness of the samples of the material used. Two methods are shown. The characteristic frequency can be approximately determined by finding the point of intersection of the amplitude asymptotes. Another way is to fit the amplitude of the photoelastic component of the photoacoustic signal with a defined function. Apart from the explanation of the methods themselves, the paper will examine the reliability of both methods.