Sound level meter?

Does anyone know how I can build a simple sound level meter with a light that will come on at a certain sound level?

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iceng2 years ago

I seriously do not think you understand or read the LM3915 or 16 PDF.

This IC takes any audio signal and lights a dot (led) according to audio amplitude

Then an instructable

You will need an opto-isolator on each channel with the outputs in three parallel groups. For your easy, there are more pictures, including the marvelous quad IC.

There is no Best Answer for me here when you hijack an old question... A full schematic design takes more time then I want to allocate...

OPTOISO Isw.jpgQuadOpto.bmp
iceng6 years ago
Years ago I designed a classroom  traffic light always green then yellow
as the noise went up to a preset level and Red when too much  with a
beeper for a pilot school program that did not appear to work,
as I never was contacted to replicate the prototype.

dessxx iceng2 years ago

iceng do you have the electronic schematic of this project!!

iceng dessxx2 years ago

That was before cad schematic capture programs and those files are long ago gone.

Today I would use a dollar piezo mike to provide an audio signal to the LM3915 operating in dot mode and place some optical isolators to control what you are after.

microphone ceramic diag.jpgOPTOISO-Triac-Triac-sw.JPG
dessxx iceng2 years ago

thank, but I have a question how do I split in three different channel green yellow and red? At the end I need three output to light three small light bulb! DC light bulb if possible!

aelias366 years ago
Op amps:


Watch the two videos, and build the circuit in the second. Go ahead and ask about anything you're confused about.
pennsteve (author)  aelias366 years ago
What I need is to keep a group of kids from getting too loud. If they get to a certain decibel level I want a light to come on to show them they need to quiet down. lol
This is a bit dated, but wondering if you found a solution. My son has a hard time knowing when his voice is too loud (way too loud). Would love a sound meter that would let him see how loud he is.
I tried something similar when I was teaching rock climbing. Since I needed to be able to hear the climber I was belaying, it was a safety issue. No matter what I tried, nothing worked like shouting "QUIET!!!!!!!!" :) The light idea probably wouldn't work because when they are talking, they are distracted, and will not be looking at a light. A siren might work, but I really doubt it. :(

Good luck keeping the DB down! :)
And that's really going to work ... how?

Maybe if you replaced the lights with high-voltage (aluminum foil) sheets on each bus seat....
omg... really? o_0
pennsteve (author)  canucksgirl6 years ago
Yes, really.
canucksgirl6 years ago
ok then... Here's an instructable to create a light that comes on with sound. You can apparently adjust it so the light comes on at the sound level you choose.
pennsteve (author)  canucksgirl6 years ago
Unfortunately no. It is for a school bus and has to be DC. :-(
I found you a link but it's not letting me post it properly. I'll send you a PM.
pennsteve (author)  canucksgirl6 years ago
I got the PM. Thank you. I'll have to look into that.
No problem. Let me know if you need more help. :)
I sent it, you should have it in your inbox.
Will this work for you or do you need more help?
Re-design6 years ago
Try something like this.

Where it's labeled audio input, use a cheap portable, adjustable amp. and mic.  This amp and mic will pick up the noise and you adjust it to turn on your lights at the level you like.

You can sub one or more of the leds with the indicator lights that your kids will see.  You may (probably) will have to add a transistor or relay to carry the current of the larger light so you don't burn up your chip.