They use two different weighting filters required by the IEC651 and ANSI S1.4 Type 2 for audio filtering. 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 94 dB 1 kHz, etc).
What’s Included
- SM-20A
- Carrying case
- Battery (installed)
- USB cable download and software CD