CEM DT-173 USB Sound Level Meter Built-in Datalogger Noise Monitor Data Logger 31.5HZ ~ 8KHZ 30dB ~ 130dB (Black) Conforms to the IEC61672-1 Class 2 for sound level measurement NORM and PEAK mode ; Over range indication A & C frequency weighting Fast (125ms) and slow (1s) time weighting Calibration via software ; Manual and automatic start modes