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Spectral resolution of FFT in a acoustic simulation |
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March 2, 2022, 10:52
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Spectral resolution of FFT in a acoustic simulation
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#1 |
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New Member
Join Date: Jul 2021
Posts: 10
Rep Power: 4  |
Hi everyone, I am trying to simulate the tonal noise of a centrifugal fan (with FW-H analogy model) and have a problem with the Post-processing.
To represent the tonal noise I have created a FFT but it seems that there are too little data points hence the resolution of the graph is not sufficient. I have tried decreasing the time step but to no avail. Is there something that I have missed? Additional info: I have set the write frequency in the acoustic sources tab to 1 Last edited by Leoma; March 2, 2022 at 10:53. Reason: Additional picture |
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March 2, 2022, 12:03
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#2 |
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Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,672
Rep Power: 65 |
Resolution is limited by how long you record the signal, so run your simulation longer if you want more resolution. If say this data corresponds to time = 0 to 1 seconds of physical time. Run it for 2 seconds.
Maximizing the sampling frequency by setting it to 1 merely allows you to to reach a higher maximum frequency on the FFT (i.e. the range). It doesn't improve resolution. |
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March 7, 2022, 11:11
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#3 |
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New Member
Join Date: Jul 2021
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Thank you!! I finally get it. I still have one question. My frequency max is set to 10 kHz. Do you know how to increase it?
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March 7, 2022, 14:33
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#4 |
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Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,672
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What's your time-step size? Is it 1e-03 seconds?
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March 7, 2022, 16:12
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#5 |
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New Member
Join Date: Jul 2021
Posts: 10
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5e-5 seconds
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| Tags |
| acoustic analogy, fft, fwh |
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