EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: jorenca on August 09, 2016, 08:43:19 pm
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Hi forum,
I'm trying to build a simple LED bracelet that would light up when (very loud) ambient music has
lots of bass in it (for example, when the beat 'drops').
However, I encountered the problem where the microphones in my junk bin are all 'telephone' grade ones -
that meaning with a small bandwidth, most likely outside the range of 20-200Hz.
I started wondering if I could use some reed switch to register the sound, but it seems reed switches
have a resonant frequency of about 8kHz.
Can you propose a sensor to be used, seeking maximum simplicity and low energy consumption?
(you may have guessed that I'm building a glowing party bracelet and the overall size is the main limiting factor)
Thanks!
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Maybe a place to start would be designing a mechanical circuit that has a resonance peak near the range you're interested in? You'll want something with a large surface area that can be sensitive to bass vibrations, without being affected by body motion.
If you can create a mechanical surface that's sensitive enough to the bass, you may be able to pick up those vibrations with piezo.
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Use an electrect microphone capsule which should be fairly sensitive to bass.
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... and a low pass filter ... etc.
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Here is the frequency response of an ordinary electret mic. It goes lower than 20Hz but the graph stops at 25Hz. A cheap one measures a little different at high frequencies.