What is SEL?
The sound exposure level averages the sampled sound over a second period. Assuming the sampled run time to be greater than one second, SEL is the equivalent one second noise that would be equal in energy to the noise that was sampled. SEL is typically measured using a 3dB exchange rate without a threshold. (SEL is not used by OSHA). Example: Suppose you wanted to measure in a location next to railroad tracks which also happend to be in the takeoff path of an airport. A train passes by taking 10 minutes with an average sound level of 82dB. A jet passes overhead taking 45 seconds with an average sound level of 96dB. Which of these events results in more sound energy? You can answer the question by comparing their SEL readings, which compress each event into an equivalent on second occurrence. (SEL for the train = 109.7dB, SEL for the jet=112.5dB).
