Be aware that phone microphones have a cutoff feature, so sudden loud noises aren't picked up. Sudden and loud like a shot from an airgun. The downloadable decibel meters work in normal circumstances for background noise, but due to the cutoff circuitry in the phone, they really can't (in my opinion) give accurate readings for sudden loud noises, like an airgun. Take it for what it's worth, but I haven't found a downloadable app yet that really worked for me.