Sound Level Meter: Sound Level Meter (SLM-04) is designed according to the specification outlined by West Bengal Pollution Control Board. This is a type-2 sound level measuring instrument useful for measurement of sound / noise level at public place, factories, workspace etc. It is a battery operated handheld instrument having a suitable carrying case. The instrument provides 500ms and 200ms time weighted reading of sound level which is selectable through front panel switches. Leq measurement can be done for a fixed time interval of 1-30 minutes, with one minute resolution. A Graphic LCD display shows the readings. Active filters are used for implementation of A & C weighting frequency characterization. Two selectable measurement ranges are available: Low (40dB - 90dB) and High (80dB - 130dB).