I bought this to measure sound levels. During the day, the lowest db level recorded was 65 db. I happened to wake up at 2 one morning, so I tried the sound levels then. The lowest reading was 64.7 db. My neighborhood is rather quite at 2AM.My research tells me a typical library is 40 db, so my house at 2 AM should be in the 20 db range. When the refer cycled, the noise level, according to this meter, stayed at 64.7 db. Sixty-five decibels is the noise level of a fairly loud office, not a quite neighborhood at 2AM.I contaced the company about calibration. Their response was that the service was not available.That makes my purchase a waste. If the sound readings are so far off, how can I trust it to be accurate anywhere else?