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I am working on a senior design project that involves regulating the noise from headphones to make sure no damage to the ear is done. I have all parts working except the part necessary to switch the unregulated audio input to a regulated one which would turn the sound level down. I have tested Solid state relays, and am currently trying to use a digital potentiometer to automatically increase the resistance of the audio like to decrease the sound. Could I use an H bridge also to switch between two possible outputs (no resistance vs resistance) and if so should I?

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    \$\begingroup\$ What you should do is create an AGC design or a soft limiter using feedback. \$\endgroup\$ – Sunnyskyguy EE75 Apr 23 at 21:29
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    \$\begingroup\$ H-bridges are used to allow a circuit to drive current through a load in both directions so it is inapplicable here. \$\endgroup\$ – Toor Apr 23 at 22:08
  • \$\begingroup\$ How do you intend to quantify the limit point since that depends on the transducers within the headphones? \$\endgroup\$ – Paul Uszak Apr 23 at 22:12
  • \$\begingroup\$ @PaulUszak I’ve created an equation that relates the applied voltage to the earbuds and the respective decibel output, and then just built a multimeter with arduino that uses that equation. I sample a voltage every 10 ms and integrate with that time interval. Once the Db*s exposure reaches a value specified unsafe by OSHA, I intend to decrease the volume in some way. Actually works much better than I thought. \$\endgroup\$ – Jake Blocker Apr 23 at 22:21
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    \$\begingroup\$ Just use a relay if it's a school project. Might have to be a dry switching relay, and never run it wet or else it may not be able to conduct dry signals anymore. Dry is a low-current signal, wet is high current. Arcing when interrupt higher currents produces corrosion which inhibits low voltage, low current signals from being able to punch through. \$\endgroup\$ – Toor Apr 23 at 22:56
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You could use three DPDT relays to get 4 sound levels on two channels:

schematic

simulate this circuit – Schematic created using CircuitLab

I don't expect you'd be able to get it to respond fast enough to protect hearing in something like a shooting range though. It might be okay for something like an aircraft mechanic.

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