Integrating Sound Level Meters : In earlier times the instantaneous sound pressure levels were Exponentially averaged in an RMS detector of limited dynamic range and the results were further dependent on the selected meter Time-constant settings, so a series of measurements could not be combined to get the overall result. The only way to 'record' and 'measure' time histories was to connect the meter output voltage to a Logarithmic level recorder and plot the dB level vs time histories. With the advent of digital techniques it was possible to integrate the sound levels over a wide dynamic range, use Linear averaging circuits over long measurement periods and the Integrating-averaging Sound Level Meter was 'born'. Now commonly known as the Leq or Equivalent Continuous Sound Level Meter
Integrating circuits also greatly enhance the accuracy and dynamic range of Statistical Noise measurements.
To see a range of Integrating Sound Level Meters click HERE.