shifting peak frequency

[Jaty22]

Many thanks, Doug,

I have shared the code and other information in a pdf file except for the data.

Kind regards

Jaefer

[santo_13]

If less than 10sec capture does not reproduce the issue, I would suspect it is your signal shifting. I am not familiar with your application to comment if it is expected for the signal to shift in frequency over time.

I guess you're trying to create a spectrogram (time vs frequency spectrum) and a real spectrogram/sonograph plot would make better sense than multiple plots for each segment of capture.

[Henrik_Volkers]

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@Jaty22 wrote:

Thank you, Henrik,

I don't expect any frequency shift.

Happy weekend to you too.

Jaefer

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Well, we don't know your setup, but if I think of a tank with a liquid (water) and a bubble source (air tube with nozzle), some influences come into my mind:

1. temperature change-> viscosity (or other properites of both media)  change -> rate change   and/or  the nozzle diameter will change with temperature

(whatever setup you (one) build, if you look close enough, you always build a thermometer :D)

2. turbulences/streams. your bubbles or other sources (temp 😉 , ...) create streams in the water, that also can have an influence of the physics on how the bubble comes off the nozzle

3. you need a stable air/gas pressure ... if you measure (coarsly) the frequency to pressure ratio you get an idea on how stable your pressure needs to be.

4. Any  vibration in the tank /nozzle will have an effect.  Your water tank has it's own resonances (more than one mode) .. your bubbles will exite these resonances .. maybe you see some beat frequencies 🙂

5. ??? 

time for my first coffee 😄