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Measurement of the resonance curve (Acoustics)
#61
A simple fix apparently is 1 –> 2 in
Code:
        <if less="true" equal="true" greater="false">
            <input as="a" clear="false">run</input>
            <input as="b" type="value">2</input>
            <input as="true" clear="false">fft2500</input>
            <input as="false" clear="false">FFTaverage</input>
            <output as="result">FFTaverage</output>
        </if>

However, the number of runs is off by two then. I am a bit unsure how to properly fix it as the analysis block is run like

  1. on initialisation, before tapping play,
  2. after tapping play, without audio data,
  3. and higher: “regular” runs are starting
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#62
The “cycle” attribute looks like a quick fix. A proper solution would be checking the buffer length if there is sufficient data for a first run…
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#63
Dear Jens,
I just have found this problem. A new version has to be published where this bag is corrected.
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#64
Hi,
I have added the following before the block shown by Jens and it works:

<!-- 2023 -->
<count>
            <input as="buffer" clear="false">fft2500</input>
            <output as="count">count</output>
</count>
        <if less="true" equal="true" greater="false">
            <input as="a" clear="false">count</input>
            <input as="b" type="value">0</input>
            <input as="true" type="value">0</input>
            <input as="false" clear="false">run</input>
            <output as="result">run</output>
        </if>
So run remains zero until appearance of fft2500...

Example is a tube of 23 cm length with open ends.

Best
Mikhail


Attached Files Thumbnail(s)
   

.phyphox   resonance_white_FFT2500c.phyphox (Size: 5.4 KB / Downloads: 140)
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#65
Hm… I still obtain “Runs 1” before I tap play, both on Android and iOS. Is this on purpose?
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#66
I am also surprised where it comes from...
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#67
Dear @solid,

thank you for the wonderful experiment. I tried as acoustic resonator and it worked perfectly. Both, the sweep option and the FFT.
Then i thought, this could be wonderful for High-/Lowpassfilter with RC. I built one with C=100nF and R=1000Ω.
I can measure the damping (see attached) figure with an oscilloscope, but didn't suceeded with an audio option.
My idea was to use a 3.5 mm 4-conductor and use and audio chanel R and the microphone pin AUX.
But no success. Sometimes it was misinterpreted by the phone as signal to reduce the volume.

Have anyone an idea?


Attached Files Thumbnail(s)
           
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#68
Dear J-Almer,

maybe your smartphone is too modern, it is better to use old models for this experiment. Your proposition worked perfectly well. I have chosen  R = 10 kOhm and C = 0.1 µF for the characteristic frequency 1/RC = 1 kHz.


Attached Files Thumbnail(s)
       
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