(02-08-2021, 02:15 PM)Jens Noritzsch Wrote:(02-07-2021, 04:14 PM)paul.davies@york.ac.uk Wrote: I have had some trouble with the white noise generator. It seems to have some artifacts in the spectrum and responds differently with different phones.
Could you provide us with examples so that we could have a look into it. We would suspect audio (speaker) characteristics of smartphones rather than a software bug…
The Fourier transformation technique with the white noise excitation gives the same spectrum as the frequency sweep technique, so I think everything is OK with the white noise generator. The spectrum depends on the positions of the source and the detector. The best results are obtained when the source (earphone) and the microphone are inside the tube at a distance of approximately 3 cm from its end..
We have started to prepare the acoustic resonance experiments for large first year student labs and found some faults in the programs posted here at #36: the frequency scan experiment gave interrupted signal for iOs and the white noise Fourier experiment gave too high peaks at 0, 50 and 100 Hz for some phones. In order to correct the first fault the tone generator was configured with loop="true". For the second the Fourier experiment was limited by 200 Hz at low frequencies.
All is OK for Android, iOs is still to check...