How accurate are smart phone SPL meters?

[BlueGreene]

I ran a show last night for two funk bands in a room that was around 24' wide and around 40' long. High ceilings with some corner conditioning but a brick wall on one side and drywall on all the others. The staging was 16' wide and half was 8' long and the other half 12' long. There was three or four horns, bass amp, guitar amp and keys amps with three vocal mics, drum set and percussions. Filled up the mix wiz I was using. It LOUD AS F#%$!. I would have pegged it at (the FOH booth and all over the room frankly)  around or over 100 dB but my assitant's smart phone was regestering it at 92-93. dB. It was a nokia or something. These apps seem to be popping up on all the brands. Are there particular models that are more accurate and/or are the same programs writtin for different model phones? And does anyone know how and if they are calibrated? Does anyone have a model/app that has been tested against relyable test equipment? 

[agedhorse]

Do you know what the filter was? The averaging time constant? The max spl that the mic will handle before the internal limiting occurs?

 

These are all critical bits of missing info.

[Pro Sound Guy]

The easy way would be to compare the phone to an accurate measurment tool.

 

 

 

[fdew]

 

I have done some research on this  as I was looking for a good SPL app for my Ipad.  There are two limits to making a accurate SPL app.  One is the quality and repeatability of the mic. this will cause the app to always read high or low or not be sensitive to certain frequency.  A biger problem is that many phones and pads have designed in "features" to limit SPL so the phone may be pretty good up to a point and then show almost no change above that level.  I beleave that you witnessed this problem.

 

Also, there is a big difference from device to device.  Some are much better for a SPL meter then others. 

 

Here is just one article on the subject.

http://www.tvtechnology.com/prntarticle.aspx?articleid=211051

[agedhorse]

Possibly room interactions?

[Craig Vecchione]

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agedhorse wrote:

Possibly room interactions?

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I put two other speakers in the same position, and don't get the same effect or odd readings. I moved everything to another position, same set of results. I also lowered the levels to reduce the effects of the room, same thing of course at lower levels.

What's interesting is that this particular speaker has a reputation for this response issue. I thought it would be interesting to see if there was any truth to the rep, heard it, and then can't really seem to quantify it. Of course, a legitimate dB meter would be a lot more useful in this regard.