If you know the structure of the “tick”, you can apply the technique of a correlation receiver. It can dig up signals below the noise floor and is used in GPS reception.
replyAwesome writeup! I wonder whether with a real contact mic (Korg offers one for about 20 bucks) you could get much better results. Due to no 3,5mm on phones anymore it might be easier to use a sound-enabled SBC though.
replyDid you consider trying the iPhone accelerometer? Perhaps lay the phone face down on the table and then lay the watch on the back? Wondering if this would have higher or lower SNR.
replyI don't think it would work because the accelerometer updates are at too low a frequency. Apple's developer info says:
reply``` Before you start the delivery of accelerometer updates, specify an update frequency by assigning a value to the accelerometerUpdateInterval property. The maximum frequency at which you can request updates is hardware-dependent but is usually at least 100 Hz.
```
100Hz is way too slow. Presumably some devices go higher but according to the article the peak signal is in the 3kHz to 15kHz range.
How does it compare to other apps ("watch accuracy meter" for example) on android?
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