After extracting the signal power, the calculated sound levels are low-pass filtered (smoothed) using an adjustable time constant. This time constant is applied to the calculation of L-min and L-max, but not Leq. A typical short time constant (125 ms and lower) allows the measurements to track sharp changes, while a longer time constant (1s and longer) provides more stable (cleaner) RMS values that average short transients.

 

The Leq is integrated linearly over the specified log interval.

 

The sound level statistics (L-min, L-max and Leq) are gathered for the specified log-interval before being written to the recording memory. The log-interval represents the interval at which the selected statistics are written to memory. Therefore a longer log-interval uses less memory, while a shorter log-interval provides better time resolution and allows the user to distinguish between events that occurred close together. The statistics (L-min, L-max and Leq) are reset at the beginning of each log-interval. Then the statistics are gathered sample-by-sample during the log-interval. At the end of each log interval the calculated statistics are written to memory, and the next log-interval is started. No portion of the signal is overlooked.

 

The log interval is set to 1 second by default. It can be set to as short as 1/8 s.

 

Note: The time constant only affects the calculation of Lmin and Lmax. The Leq is integrated linearly over the specified log interval.