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Having a dB meter is useful for when you want the traces of your frequency response measurements to appear at the correct dB SPL. Also useful for just checking whether you are listening too loud. Buying a stand alone SPL meter can be costly though. So I've always liked the thought of having a reasonably accurate dB SPL meter on my iPhone. I've downloaded and tried a few but I always had my doubt regarding the readings.
Googled and found these articles:
http://www.safetyawakenings.com/safety-app-of-the-week-42/
http://blogs.cdc.gov/niosh-science-blog/2014/04/09/sound-apps/
http://scitation.aip.org/content/asa/journal/jasa/135/4/10.1121/1.4865269
Basically it seems the app to get is SPLnFFT Noise Meter. It's on the Apple App Store for R54. https://itunes.apple.com/us/app/splnfft-noise-meter/id355396114?mt=8
"Our highest rated app is the SPLnFFT app (see below image) for $3.99. During the four tests we conducted, this was the only app to absolutely nail the results each and every time. It passed all four tests with flying colors. In fact, this app’s results were so close to the results obtained using the $2,000 noise meter (3M/Quest Model 2200 SLM) that the tiny differences between the two are probably due to sampling error. We do have one major concern about this app – it will only measure noise up to a maximum of 94 decibels!"
I'm not sure what the Android guys can use, but it's probably quite difficult to create an Android SPL meter app that is accurate on all the different hardware Android is available on.
Obviously the iPhone mic isn't flat, I'm assuming coded into the SPLnFFT Noise Meter software they have a generic calibration file for the iPhone transducer to increase the accuracy of the measurement.
There is also this Dayton audio calibrated mic add on for iDevices that looks interesting.
http://www.daytonaudio.com/index.php/imm-6-idevice-calibrated-measurement-microphone.html
Using a mic like this could alter the measurement results of the software though, so I'm not sure how one would integrate it. I guess whichever app you use it with has to have an appropriate gain or attenuation stage, specifically for that mic, as the input voltages from the onboard mic might be higher or lower in comparison to the add on mic. Not to mention that one would have to bypass the iPhone's built in mic calibration file (if such an adjustment does exist in the software) and load the Dayton audio mic's calibration file.
Dayton talk you through how to use their mic with the AudioTools app (from Studio Six Digital) for iPhone and the AudioTool by Bofinit Corporation app for Android. I haven't researched the accuracy of the readings when using this mic in combination with these apps. Though one has to ask why spend $40 on a add on mic if the measurements using the OEM iPhone mic with SPLnFFT Noise Meter are already quite accurate when compared to the $2000 meter mentioned earlier in this post.
Here are some other add on measurement mics for phones:
http://www.mic-w.com/product.php?id=3 These micW ones look very nice, they also have some other models (cardioid, shotgun, boundary, XY stereo) for audio recording via mobile.
And finally there is this one too http://www.studiosixdigital.com/audio-hardware/itestmic/
Googled and found these articles:
http://www.safetyawakenings.com/safety-app-of-the-week-42/
http://blogs.cdc.gov/niosh-science-blog/2014/04/09/sound-apps/
http://scitation.aip.org/content/asa/journal/jasa/135/4/10.1121/1.4865269
Basically it seems the app to get is SPLnFFT Noise Meter. It's on the Apple App Store for R54. https://itunes.apple.com/us/app/splnfft-noise-meter/id355396114?mt=8
"Our highest rated app is the SPLnFFT app (see below image) for $3.99. During the four tests we conducted, this was the only app to absolutely nail the results each and every time. It passed all four tests with flying colors. In fact, this app’s results were so close to the results obtained using the $2,000 noise meter (3M/Quest Model 2200 SLM) that the tiny differences between the two are probably due to sampling error. We do have one major concern about this app – it will only measure noise up to a maximum of 94 decibels!"
I'm not sure what the Android guys can use, but it's probably quite difficult to create an Android SPL meter app that is accurate on all the different hardware Android is available on.
Obviously the iPhone mic isn't flat, I'm assuming coded into the SPLnFFT Noise Meter software they have a generic calibration file for the iPhone transducer to increase the accuracy of the measurement.
There is also this Dayton audio calibrated mic add on for iDevices that looks interesting.
http://www.daytonaudio.com/index.php/imm-6-idevice-calibrated-measurement-microphone.html
Using a mic like this could alter the measurement results of the software though, so I'm not sure how one would integrate it. I guess whichever app you use it with has to have an appropriate gain or attenuation stage, specifically for that mic, as the input voltages from the onboard mic might be higher or lower in comparison to the add on mic. Not to mention that one would have to bypass the iPhone's built in mic calibration file (if such an adjustment does exist in the software) and load the Dayton audio mic's calibration file.
Dayton talk you through how to use their mic with the AudioTools app (from Studio Six Digital) for iPhone and the AudioTool by Bofinit Corporation app for Android. I haven't researched the accuracy of the readings when using this mic in combination with these apps. Though one has to ask why spend $40 on a add on mic if the measurements using the OEM iPhone mic with SPLnFFT Noise Meter are already quite accurate when compared to the $2000 meter mentioned earlier in this post.
Here are some other add on measurement mics for phones:
http://www.mic-w.com/product.php?id=3 These micW ones look very nice, they also have some other models (cardioid, shotgun, boundary, XY stereo) for audio recording via mobile.
And finally there is this one too http://www.studiosixdigital.com/audio-hardware/itestmic/
