Pretty good

I agree with the other reviewers that the interface could use a little more, but on the whole it seems to be fairly accurate. I was testing it while mixing at church. A fast response would be nice. Also an "A" and "C" weighting switch would be very helpful since the mic picks up the frequencies different from your ears. (ie. A Bass guitar might have an absolute sound pressure of 85db but your ears would hear it at 75db). But all in all, I like it and appreciate that its free!

Mike Gauer about Decibels: dB Sound Level Meter