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Noise cancelling a fan
To get more comfortable air quality.
I have this big 20 inch Lasko box fan and it's loud to the point of being annoying when I set it on max level, and so I don’t. However, when I listened to my fan more closely, I realised that there was a droning low tone that sounded like a constant frequency. Using my laptop microphone, I wrote a rough script to get the dominant frequency of the fan via a recording and then Fourier transforming it.
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