Bass (low frequency) sound detection?

[jorenca]

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!

[scanlime]

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.

[Zero999]

Use an electrect microphone capsule which should be fairly sensitive to bass.

[Brumby]

... and a low pass filter ... etc.

[Audioguru]

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.