Comment on Magnetic bass detection?
alzymologist@sopuli.xyz 4 weeks ago
Could be doable with just a hall sensor chip, you have one in your phone, just check it out quickly. Large coil will probably catch slow vibrations too. Also try just filtering audio signal, like get only sustained bass sound, footsteps and voice have short lived low frequency components compared to most music except for percussion I suppose.
I tryed with the magnetometer in my phone before and sadly it didnt pick up anything, i think the polling rate may be to low too. But ima search around for some more sensitive hall effect sensors
Ok, I’ve done experiment myself; it was a dumb idea. Sure I can see the bass beat on smarthone hall sensor as sharp periodic spikes… from few cm away of the coil.
Thing is, any measurable signal outside of coupled system is essentially power loss, which industrial made speakers are, obviously, optimized against. The field loops back into the magnetic drive through the shortest achievable path. Then, it’s not your typical radiative EM system, it’s low frequency near field transmission - field drops exponentially as you move away from the coil.
Most probably, you’d need to measure long periodic signal, do lots of oversampling, etc. to gen anything. Or build a high fidelity resonator to steal the field from the speaker - essentially, same thing, except the resonator will probably start singing, too.
So I’d give up on magnetic approach; why go for counteroptimized signal when you have optimized acoustic field? Just analyze it - look for sustained harmonic vibrations, fat envelopes so different from human voice barking and foorsteps; EDM are full of those nice sounds.