05-08-2020, 04:01 PM

Hi,

I always wanted to look closer at the determination of the resonance by FFT. It is strange, when you repeat the experiment , the resonance frequency f0 remains exactly the same ??!.. I have found a very similar but not exactly the same graduated cylinder (nominative 250 mL) but I got exactly the same f0... So, I have plotted the resonance part of the measured FFT spectrum together with direct measurements of the resonance by frequency sweeping (see 'acoustic resonance' in this forum). The interval between points in FFT is very large (46.875 Hz) and a good result can be obtained only by chance. This is also the answer to some questions asked here earlier. In order to reduce this interval we have to increase the time of the sound treatment..

I always wanted to look closer at the determination of the resonance by FFT. It is strange, when you repeat the experiment , the resonance frequency f0 remains exactly the same ??!.. I have found a very similar but not exactly the same graduated cylinder (nominative 250 mL) but I got exactly the same f0... So, I have plotted the resonance part of the measured FFT spectrum together with direct measurements of the resonance by frequency sweeping (see 'acoustic resonance' in this forum). The interval between points in FFT is very large (46.875 Hz) and a good result can be obtained only by chance. This is also the answer to some questions asked here earlier. In order to reduce this interval we have to increase the time of the sound treatment..