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Full Version: Measurement of the resonance curve (Acoustics)
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Ups, should have actually tested the QR code. The forum did not allow viewing attachments as a guest and of course phyphox is not logged into the forum when access the file. Took me a while to figure this out, but now it should work.
Unfortunatly, for now this experiment can't export the data.
I tried to add new elements in the export menu with the editor in order to export the data but i failed... I tried a few things like to disabled some of the clear option of the buffers but it didn't work...
Can you help me ?
(01-07-2020, 10:35 PM)julien Wrote: [ -> ]Unfortunatly, for now this experiment can't export the data.
I tried to add new elements in the export menu with the editor in order to export the data but i failed... I tried a few things like to disabled some of the clear option of the buffers but it didn't work...
Can you help me ?

I think i have found out how do to it. That was easy in fact.
Great to hear - this saves me one item on today's todo list Smile
Let me know if something is still unclear.
I am happy to see how popular became this topic.

Unfortunately, there are still 2 problems to be solved:
1. A delay between the given frequency and measurements (about 2 Hz with current parameters)
2. A crackment with changes of frequency (Sebastian, have you developed a generator module ?)
Both should be solved with our new integrated tone generator, which I hoped to implement for the latest update. Hopefully I get to it for the next one...
I have slightly modified the program after version 3 obtained by Julien in order to have "infinite" measurements (now version 4). So, I measured not only an isolated resonance of the Helmholtz resonator (100 ml Erlenmeyer flask) studied at the beginning, but also a PVC tube closed at one end which gives a series 1:3:5 harmonics corresponding to the standing waves. I obtained the expected peaks (see the screen capture) but their heights were growing ruffly proportional to the frequency. I wonder if this is not an artifact of the signal treatment in the phyphox program. In the attached figure I have divided the signal by frequency (upper panel is the acoustic response of the Helmholtz resonator and lower panel is the corrected response of the tube)... Evidently the 1/f correction can be introduced to the acquisition program, but it has to be first understood (the phyphox program was developed from the given examples).
[attachment=98]  [attachment=99]
Do you see the f-dependency without the resonator? If this is a problem of the experiment, just the sound without any resonance should show the same behavior. I just had a look at the file and it does not really do much, that could have an effect here. It creates a sine function that is sent to the speaker and the amplitude analysis is even simpler - it is the sum of the square of each sample.

I could imagine that the frequency dependencies of the speaker and mic might play a role here.
Few weeks ago I did this experiment with a 250 ml graduated cylinder and an open tube at both ends, 40 cm long and 28 mm in diameter.
I also told myself that the frequency dependencies of the speaker and the microphone could play a role here.

[attachment=100]

[attachment=101]
(04-13-2020, 09:33 AM)julien Wrote: [ -> ]Few weeks ago I did this experiment with a 250 ml graduated cylinder and an open tube at both ends, 40 cm long and 28 mm in diameter.
I also told myself that the frequency dependencies of the speaker and the microphone could play a role here.
I had to think about this myself. In addition to this the frequency response depend from relative positions of speaker and microphone and theirs  positions inside the tubes. Some corrections in the following figure: upper panel - microphone and speaker outside the resonator, lower panel - the frequency response of the tube closed at one end corrected by upper curve..
[attachment=102]
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