How accurate are noise meter apps on the iPhone?
Just thought I would check to see how loud my car was after fitting a new airbox & the "How Loud" app registered between 98-99 decibels
@ 7500rpm
How confident would you be going to a track with a 100 decibel limit after that?
Cheers
Iain
Not very
The mic on an iPhone is very basic and the software not calibrated
It's a guide only
Some are pretty accurate. I'm an audio professional, and use JL Audio's app that has an SPL meter, it tracks my standard SPL meters quite well. I've also got a computer program called SMAART that I use to monitor various gigs I do, and the JL Audio is normally within a dB of what I measure with the whole SMAART rig.
I borrowed a calibrated meter recently and compared it to my iPhone 4 app. At normal office levels it was out by about 12%.
So not very accurate unfortunately.
Rich
I've seen 3 different phones running the same app say next to each other reading totally different values. Never compared them to a calibrated
meter but 2 out of the 3 would have to be out. So not very.
[Edited on 19/5/13 by coyoteboy]
I found my iPhone sound level app (SPL Meter) was spot on but you need to ensure you use a very similar distance and angle to the exhaust pipe as will
happen in the real test. You also need to ensure that the exhaust gases are not "blowing" into the mic so you might need a muffler on the
microphone. Remember to test the car at the correct RPM as well.
Let's put it this way, it's a lot more accurate than the typical human ear so should be better than nothing. If you want greater accuracy
then you might need to use a larger, more accurate microphone which you can do. Some sound level apps even have settings to accommodate some of the
popular external mics.
C.
[Edited on 19/5/2013 by craig1410]
quote:
Originally posted by scottfraser
Some are pretty accurate. I'm an audio professional, and use JL Audio's app that has an SPL meter, it tracks my standard SPL meters quite well. I've also got a computer program called SMAART that I use to monitor various gigs I do, and the JL Audio is normally within a dB of what I measure with the whole SMAART rig.
quote:
Originally posted by Confused but excited.
quote:
Originally posted by scottfraser
Some are pretty accurate. I'm an audio professional, and use JL Audio's app that has an SPL meter, it tracks my standard SPL meters quite well. I've also got a computer program called SMAART that I use to monitor various gigs I do, and the JL Audio is normally within a dB of what I measure with the whole SMAART rig.
As db is measured on a logrithmic scale, within 1db isn't that accurate. A difference of 3db is a difference of 10 times in noise level.
Never really thought about it with regard to track levels, but is it also A loaded when they measure it, same as when it's measured in a working environment?
quote:
Originally posted by Confused but excited.
quote:
Originally posted by scottfraser
As db is measured on a logrithmic scale, within 1db isn't that accurate. A difference of 3db is a difference of 10 times in noise level.
Never really thought about it with regard to track levels, but is it also A loaded when they measure it, same as when it's measured in a working environment?
I thought that a 3db difference was roughly twice or half the noise level depending on which way you are looking at it.
MikeRJ - 19/5/13 at 02:11 PMquote:
Originally posted by Ivan
quote:
Originally posted by Confused but excited.
quote:
Originally posted by scottfraser
As db is measured on a logrithmic scale, within 1db isn't that accurate. A difference of 3db is a difference of 10 times in noise level.
Never really thought about it with regard to track levels, but is it also A loaded when they measure it, same as when it's measured in a working environment?
I thought that a 3db difference was roughly twice or half the noise level depending on which way you are looking at it.
3dB gives you a doubling (or halving) of sound power.
6dB gives you a doubling (or halving) of sound pressure level.
However, since the human ear has a logarithmic response to SPL, it actually takes an SPL change of approximately 10dB for a perceived doubling (or halving) of volume level.
MikeRJ - 19/5/13 at 02:15 PMquote:
Originally posted by enginearin
The reason that they are so good for audio apps is that the signal path is consistent between devices, hence APP developers can guarantee the app performance.
I very much doubt the iPhone was ever designed to have a particularly close tolerance on the gain of the signal path. It would mean high precision resistors and capacitors would be required, coupled with a calibrated microphone which would add a lot of unnecessary expense.
[Edited on 19/5/13 by MikeRJ]
craig1410 - 19/5/13 at 04:02 PMSome useful info here on iPhone Mic performance from the company who produce SPL Meter (the one I use):
http://www.studiosixdigital.com/iphone_hardware/iphone_3gs_microphone.html
Note what they say about iOS versions prior to iOS 6 having a low pass filter which can now be switched off by the application for iOS6 upwards. This is probably quite important for measuring sound level of a car engine which will have some low frequency sounds for sure. If you have access to a calibrated SPL meter then you can also calibrate this app.
Also some good info on an external fully digital interface Mic here:
http://www.studiosixdigital.com/itestmic/itestmic.html
"When you plug iTestMic into any iOS device running AudioTools, the factory calibration values are read and applied, giving you an instantly available accurate SPL measurement tool calibrated to +/-0.1 dB, no matter what iOS device you are using." - Sounds like a bold but confident claim. If you read some of the stuff on this website it certainly sounds like these guys know what they are doing and the app is aimed at audio professionals and has good reviews so maybe it works pretty well.