Measurement of the resonance curve (Acoustics)

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The idea is to measure the acoustic resonance curve of a Helmholtz resonator.
The frequency of the output signal from an earphone put directly into the resonator (see figure) should be sweep between two values and the sound intensity should be measured by a microphone (also put to the resonator).
I did not find how to sweep the frequency by itself and realized a code using the phyphox editor (‘Resonance 2(3).phyphox’) with the time t taken from the timer module and a calculation of the frequency via f = f_start + df*t…
The realized program has two fails:
1. The peak position is delayed by some Hz (a problem of the synchronization of the sound reading and generation).
2. At the peak there is an instability of the registered sound intensity.


Remarks:
1. For the phyphox code I was inspired by the given phyphox experiments.
2. I find that my problem is similar to a problem given in the forum in German: ‘Frequenzgang eines Lautsprechers messen’.


Attached:
1. Phyphox code.
2. Obtained screen.
3. Photo of the experiment.