That's better than I would have thought, and in some cases on par with very low cost (sub-$50) dedicated SPL meters.
I have a side business that does audiovisual services, and I've been meaning to get the other folks in the crew to test their phone with one of these apps against my SPL meter (which is a ~$80 unit that I believe is pretty accurate in most circumstances), so they'd have a ballpark idea of how loud they're running the gear (there are noise ordinances that we sometimes have to take responsibility for following).
I'd be curious how well a phone could act as an RTA, as well. I used to use my Amiga to do analysis (non-realtime, but reasonably useful in a time when having a high resolution spectrum analyzer was amazing), and standard PCs have been able to act as RTAs for at least 15 years, so I'm absolutely certain the processing power needed is there in modern phones and tablets, but the mic and audio interface would be a limiting factor.
Maybe you could get an idea of the accuracy by e.g. feeding white noise to the phone and seeing how flat the spectrum is? And though I've never used them personally, I hear there are some pretty good clip-on microphones for smartphones on the market.
I have a side business that does audiovisual services, and I've been meaning to get the other folks in the crew to test their phone with one of these apps against my SPL meter (which is a ~$80 unit that I believe is pretty accurate in most circumstances), so they'd have a ballpark idea of how loud they're running the gear (there are noise ordinances that we sometimes have to take responsibility for following).
I'd be curious how well a phone could act as an RTA, as well. I used to use my Amiga to do analysis (non-realtime, but reasonably useful in a time when having a high resolution spectrum analyzer was amazing), and standard PCs have been able to act as RTAs for at least 15 years, so I'm absolutely certain the processing power needed is there in modern phones and tablets, but the mic and audio interface would be a limiting factor.