A method of investigation of moisture materials using FFT

A method of investigation of moisture objects, made of porous materials, using Fast Fourier Transform (FFT) is presented. A sound signal, which is the response to the percussive force, is registered in a digital form by a given sampling frequency, and at further stages it is subjected to analysis in a frequency field in order to determine the main formant. It is proved that the main formant position, which is the response to the percussive force, is a function of moisture changes in the investigated object. An algorithm enabling analysis of the discussed phenomenon in the MATHCAD environment is presented. The following fields may be examples of the described method and programme applicability: i) testing of hygrometers used for moisture investigations of porous materials; ii) the program prepared by Professor Bogdan Skalmierski was used much earier in diagnosis of stringed musical instruments, where the dependence between the main formant position and stress states occurs.