# Decibel level recorder for internal microphone



## MacDoc (Nov 3, 2001)

Looking for a simple free app to record and store external sound levels from the internal microphone on a MacBook pro.

*I'm curious about Db levels on the traffic noise and just wanted something I could leave running and have it record the sound levels.
*
A friend does not understand attenuation over distance.

She's a 1/2 KM away from the road and the trucks were 10' away from my unit's window.

She's wondering why I moved to a different unit 

It will actually be useful to the owners to know the decibel levels as some of the trucks are barrelling at 100km+ in a 60 km zone and are tandem rigs.

It's fruit season and they're pretty steady day and night.

I had been using the noise cancellers headphones but cannot sleep with them on and just as I drift off another truck goes by. :baby:

Much quieter location now - wish I had asked sooner but I spend so much time outside it was not all that big a deal.

Tips? Apps?/
thanks


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## irontree (Oct 28, 2006)

I remember Radio Shack used to sell a device specifically for measuring sound levels.


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## mkolesa (Jul 22, 2008)

any kind of recording you do with a microphone, whether it's the internal mic or an external one, is only going to give you relative loudness. to get an absolute sound level you'll have to calibrate the mic or use something that's already calibrated. so as the other poster has already mentioned, using something like a radio shack/the source sound level meter, especially one that will store peak levels, would be needed to do what you're looking for... but no, it's no freebie app.


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## MacDoc (Nov 3, 2001)

I just need relative as I want to move it from one unit to the other to show the difference.

traffic will tend to average out and the peaks will be lower further away.

This should work for recording over time


Audio Recorder 3.2 software download - Mac OS X - VersionTracker

Then I just need something to show the relative sound levels of the recording...

any help there??

a visual charting of the recording would be ideal.


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## mkolesa (Jul 22, 2008)

wouldn't garageband work well enough? one track could be the sound at one house and another track would be the sound at another? the vertical height of the waveforms would show relative loudness...


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## Guest (Feb 19, 2010)

You wouldn't get a very accurate measure from the built-in mics, I don't think there's any way you could properly equate a non-fixed input level to an actual db level.


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## rgray (Feb 15, 2005)

mguertin said:


> You wouldn't get a very accurate measure from the built-in mics, I don't think there's any way you could properly equate a non-fixed input level to an actual db level.


This is true. We used to use a very high end B&K sound pressure level meter in the lab. Mic characteristics vary a lot, air density changes with temperature, atmospheric pressure and humidity. If accurate db levels are expected the mic had to be calibrated every time it was used and this is for the very best of scientific equipment. We also had one of those Radio Shack meters mentioned above and it was hopeless for any serious purpose. Peak wave height in Garageband or similar for what is truly the same sound level will be different over different sessions on account of a wide variety of variables.


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## MacDoc (Nov 3, 2001)

I'm only looking for relative values - I know approximately the level of sound from a transport truck a few meters away,

SOUND LEVEL
decibels Environmental condition
140-130 Pain threshold
130-120 Pneumatic chipper (jackhammer)
120-110 Automobile horn (at one meter)
110-100 Jet aircraft overhead (low level flight)
110-90 Interior of subway train
90-80 Inside of bus, cab of a transport truck
*80-70 Busy street traffic*
70-60 Normal conversation
60-50 Office background
50-40 Living room background (suburban residence)
30-40 Library
30-20 Bedroom at night (suburban home)
20-10 Sound studio background noise
10-0 Threshold of hearing

and the flip side

The noise level drops 6 decibels when the distance doubles - 

It takes a fair distance or a fair amount of insulation to damp traffic noise and windows are not very much insulation. ;-(

I find masking noise like an overhead fan or water sounds through the speaker ( running stream etc ) seems to do the best job of reducing hearing sensitivity to traffic.

It's more curiousity than anything else at this point.


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## kps (May 4, 2003)

I have this iPhone App. Don't know how accurate it is, but I got it to check the Db levels inside the cab of my transport truck. It measures around 105-107Db with the small side window open at hwy speeds. That's inside, which does not make me all that happy.

What is your issue with the trucks, Macdoc? I seriously doubt any of them are traveling 40km over the speed limit. Perhaps you should get a laser radar unit instead of a decibel meter. Forty klicks over is just insane in a resi neighbourhood.


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## Guest (Feb 19, 2010)

You might try Audacity. I'm pretty sure that you can view the audio files after recording to see what the waveforms/levels look like if that's all you're after. It's free.

Audacity: Free Audio Editor and Recorder


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