Measuring room noise level

[Foltzmeister]

Hi all,

I'm working on a project where I need to be able to measure sound in a room up to 120dB, A and C weighted. Basically it needs to be able to sense when the noise level rises above safe levels for the human ear. I've done a little research but since I don't know squat about audio I'm hoping someone who does can help me out. My main question is what microphone should/can I use? Ideally it would be cheap and small enough to fit on a PCB while still able to measure room noise level. Any help would be appreciated.

 

[KTW]

How about a kit?
http://www.ebay.com/itm/VU-Meter-15...323?pt=LH_DefaultDomain_0&hash=item3aa2bc0d43

 

[davenn]

nice kit, but obviously not calibrated and could be inaccurate by many dB's
the OP gave the indication that it may need to be calibrated

The fully calibrated one I build that goes into clubs, pubs etc is much more expensive than a basic kit

@Foltzmeister what accuracy do you need ? and does it need to be calibrated for that accuracy ?

Dave

 

[Foltzmeister]

It would need to be pretty accurate, the user needs to be alerted if noise goes above a certain level for safety concerns. The alerting will be done by a microcontroller though, I just need a way to detect what the noise level is. I don't necessarily care about sound quality and all that.

 

[davenn]

I don't necessarily care about sound quality and all that

Yup and that's the usual situation

To get something that is calibrated for reasonable accuracy is going to cost you significant money
They sell for around AU$900 to $1200 ( Around US$700 - $900)

 

[Foltzmeister]

Couldn't you just build a circuit with a microphone then analyze the signal with the microcontroller? What part of the setup makes it so expensive?

 

[davenn]

because you want accuracy and as I said that requires calibration
The calibrator I use to calibrate my units cost $500 on its own !!

 

[Colin Mitchell]

You don' need any accurate calibration because the alarm will sound when a sustained amplitude is recorded over a period of time.
You can buy a dB instrument for $15.00 (posted) to provide a reference.
The micro kit will cost another $20.00

 

[davenn]

You don' need any calibration because the alarm will sound when a sustained amplitude is recorded over a period of time.

NO .... he needs calibration because it is what was stated as required so he knows the specific sound level

 

[Colin Mitchell]

I meant accurate calibration. Just use a $15.00 tester to provide some sort of reference.

 

[davenn]

got a link to this tester ?