SPL Alarm iPad/iPhone App ?

R

Ron Kimball

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Mar 5, 2011
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So, today I figured I'd search out and buy an iDevice app that shows the SPL in the biggest posible numbers and flashes the screen red (or something similar) when a set SPL is exceeded. Sounds like an obvious app to make, right? Well, so far I can't find one :( . Has anyone come across one? Thanks!
 
Re: SPL Alarm iPad/iPhone App ?

Ron Kimball said:
So, today I figured I'd search out and buy an iDevice app that shows the SPL in the biggest posible numbers and flashes the screen red (or something similar) when a set SPL is exceeded. Sounds like an obvious app to make, right? Well, so far I can't find one :( . Has anyone come across one? Thanks!
Click to expand...
I can't help you.

But consider what one of the biggest problems with that "concept" is.

Most phones-even with proper external mics, simply cannot take much SPL.

Around 120dB PEAK is the limit.

Yes the actual "continuous" level may be 10-20dB lower-but when the input gets overloaded-the readings are off.

So it depends on how accurate you want it to be.

And then you have the whole A/C fast/Slow issue of what is "proper". Yes a lot of people use the A scale, but if you do a little research you will find that the A scale was never intended to be used about 80 or 85dB. So when you say it was 103dBA-what you are really saying is that I am getting some sort of reading-based on these parameters-but they don't have any relation to what the SPL might actually be or the damage that it is causing on my hearing.

Yes it is a "reference", but things often get lost in what they really mean.

Again-the old simple WRONG answer-------------
 
Re: SPL Alarm iPad/iPhone App ?

The particular application in mind is a largish rehearsal studio (AKA barn loft) where the band would like to work on keeping the audience area below 95 dBa slow (?) so I think the iDevice mic would be OK. The "PA" is a pair of Bose L1's pointed at each other at the front of the stage to also serve as monitoring for the downstage talent. It's a nine piece "hobby" band (with two sax players) that wants to play some quieter outdoor gigs and needs to work on getting the three <eek> electric guitarists under control (perhaps a lost cause LOL). Idea is to set up the iPad 20 feet in front but still see from the "stage" when it goes over the limit. Would it be better to use a different weighting?
 
Re: SPL Alarm iPad/iPhone App ?

Well, on second thought I went ahead and bought that. I had purchased their stand-alone SPL Meter for a buck yesterday so "returned" that towards this. The Traffic Light sub-app has a "large" mode that displays a large SPL number and turns the whole screen grey, green, yellow, or red depending on the limits you can change - even better than the video shows :) !
 
Re: SPL Alarm iPad/iPhone App ?

Ivan is, as usual, correct in saying that the iDevices are limited to about 120 db (although Studio Six Digital says as of IOS 6 they have the ability to disable the hpf and limiter) but that is WAY over what I'm willing to submit my hearing to anyway. I am, you see, but a lowly hobbyist and can choose what I expose myself (and "my" audiences) to. Likewise as Ivan notes the accuracy of the dbA measurement does start to fall off above 85db or so but its still fairly reproduce-able and so of reasonable accuracy at the 95-100 range my normal venue "requires". So while an iDevice measurement is not accurate enough for engineering work it should suffice just fine for your stated use.

Personally I find great value in having my iPad propped at the front rail of the mix booth at my normal venue with the AudioTools split screen RTA/Spectra display running. FWIW I've been using dbA as a reference for quite a while but started getting complaints from the staff that they couldn't hear orders even when I was running at 95dbA so I looked and that often equated (with this PA in this room) to over 100 dbC -- ie. there was quite a bit of low end that the A range wasn't "seeing". So I've gone back to using dbC as a reference as it accounts for a bit more of what the staff objects to. Keeping things in the 95-100 dbC seems to keep everyone happy -- audience and management included. YMMV.

...dave
 
Re: SPL Alarm iPad/iPhone App ?

What about calibration? The app may have control over the audio interface's gain, but ultimately all it gets back from the OS is sample values. There needs to be some conversion done to get that to dB SPL, and that conversion would have been calibrated on the developer's device -- which may be a different model, different mic, different batch, even intra-batch variance is possible. Any tester without calibration is nothing more than a novelty...

Also what about the directional properties of the mic? Aren't the mics on those devices pointing towards the front or bottom of the device, but you would want the screen facing you at FoH right? So the mic would ideally be on the back, pointing at the sound source?

I'd just get a proper SPL meter, standalone unit, one with a nice bright screen.
 
Re: SPL Alarm iPad/iPhone App ?

Sean Schult said:
What about calibration? The app may have control over the audio interface's gain, but ultimately all it gets back from the OS is sample values. There needs to be some conversion done to get that to dB SPL, and that conversion would have been calibrated on the developer's device -- which may be a different model, different mic, different batch, even intra-batch variance is possible. Any tester without calibration is nothing more than a novelty...

Also what about the directional properties of the mic? Aren't the mics on those devices pointing towards the front or bottom of the device, but you would want the screen facing you at FoH right? So the mic would ideally be on the back, pointing at the sound source?

I'd just get a proper SPL meter, standalone unit, one with a nice bright screen.
Click to expand...
Good points for sure -- but the OP's original question was expressing a need for a more ballpark answer I think. There is, however, quite an extensive calibration capability in the Audio Tools app but when I "tested" my devices against a proper SPL meter they were very close -- close enough for my needs. I originally thought the same as you regarding the mic location/position on the device and where it's pointing but moving it around with pink noise flooding the room shows very little change based on direction of the mic. In short, while there are certainly more precise/accurate measurement devices available the Audio Tools app using the built-in mic is sufficient for my needs -- and it's always in my pocket to answer those questions like: "So just how loud is it when I'm driving down the road rocking out"? "Just how loud is that lawnmower / saw / router..."?

But to your point, I would not want to testify in court without having employed the external iTestMic/iAudioInterface for the measurements.

...dave
 
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