Amprobe SM-20A [3477333] Sound Level Datalogging Meter, A and C Weightings with USB and PC Software. The Amprobe SM-20-A Sound Level Meter has been designed to meet the measurement requirements of safety Engineers, Health, Industrial safety offices and quality control in various environments. The SM20A offers two types of measurements: A weighting and C weight. The A weighting is for general noise sound level and the C weighting is for measuring sound level of acoustic material control in various environments (ie 94dB 1 kHz etc...). The SM-20-A conforms to the IEC651 Type 2,ANSI S1.4 Type 2, and JISC1502 requirements for Sound Level Meters. Which means the SM-20-A uses two different weighting filters required by the IEC 651 and ANSI S1.4 Type 2: The A-Weighting and the C-Weighting audio filtering. The SM-20-A offers a PC interface.