The display shows a single number. That doesn't mean that a single range is used to get that number. Say each range has a dynamic range of 60 dB.
Start with maximum sensitivity.
Read value.
Is value maxed out?
YES - decrease sensitivity and measure again
NO - display value
It's not showing a spectrum where you can see a noise floor at 30 dB and peaks at 110 dB. Displaying a single value provides no clue what the dynamic range of the measurement is.
I have worked on a phone project once.
A low end audio ADC is 16 bit. If it was a separate IC in the phone.
It most likely is in side a large IC so the noise level might be 18 bits on a 16 bit ADC. (or worse because who cares)
I am certain there is Automatic Gain Control.
With hardware AGC a very bad ADC could have a very large range. Add 40db of variable gain in the input of the ADC .....
It could have a good ADC and the AGC is in software. Who knows.
I have some very old audio ADCs here in recorders. 16 bit is the smallest I have.
Regardless of how the the preamp and ADC are implemented, it still implies that the microphone will handle 130dB SPL linearly... which seems pretty unlikely!
A quick look at Digikey.com (small microphones) Some show noise level and clipping level. The ones I found have 91 to 96 db range. Phones likely don't have full bandwidth which will help a little. So I agree.
That is exactly my question......I would be difficult to find a transducer with such a wide dynamic range. Probably on a professional instrument, not on a mobile phone.
A cheap electret mic can have a much wider sound level range, especially much more range for louder sounds when it has the 3-wires Linkwitz modification where the common-source 2-wires Jfet inside it is converted to a 3-wires common-drain follower as is shown in this video:
That's interesting AG... thanks for posting.
The audio quality of modern phones (especially with respect to noise canceling etc) it truly impressive - don't get me wrong. It's just hard to believe that a device optimised for voice quality would give this dynamic range (especially 130dB at the top end).
Seems more likely that the progammer just read an 18-bit number and scaled it into dB's without too much considderation of how legitimate the result would be.
A bit like reading 010V on your 1% accurate multimeter and interpreting it as 10.000000V.
Real sound level meters are, of course, calibrated - there's no real way of doing that on a mobile phone. That said, I know audio professionals who use such apps (especially spectrum analysers) as very useful tools.
I have two sound level meters.
The analog one has a switch that sets the middle of the meter to read at: 120db, 110, 100, 90, 80, 70, 60db
The analog meter range is -6db through +6db.
I think the range is +126db to 54db
AND
I have a digital sound level meter.
The range is 130db to 40db.
OK these are not high end meters, but they are OK.