I assume, by the name, that the meter is reading in terms of "dBA," i.e. "dB above ambient," so the name dBA would be more correct than just dB. Picky, picky, huh? Oh well. Engineers ! To work, it would have to use the IPhone mic, and I'm wondering what the frequency response of the mic actually is? A reason for asking is that, to keep dogs off your lawn, there are gadgets that are said to emit sound in the supersonic range, say 25 KHz or thereabouts that dogs can hear but people can't. The problem with these gadgets is that you have no way to really evaluate different ones, as you can't hear what it is supposedly emitting. These gadgets cost from $12 to $150. I wonder what the upper end of the IPhone audio circuitry, and this app, is? This "dBA" meter would be a good tool to evaluate the signal level emitted by various vendors of anti-dog barkers if it goes above 20 KHz, the nominal humar ear. However, the range probably does NOT go anywhere near high enough as I would assume cell phone audio likely "tops out" at only 3 KHz or so, the upper end of many old telephone networks. But, who knows? we now have HD TV in place of black & white TV so maybe things have changed?