An hourly average of the Noise Level (HNL) including number of flights per hour N is also used and defined as: HNL = SENEL + 10 log 10 N - 35.6 (dB) A variation in the calculation ... is shown in the ...

SPL may be measured with a SOUND LEVEL METER weighted according ... in the same manner and is measured in DECIBELs. Two SPL measurements in decibels may be combined with the aid of the following chart ...

The decibel (dB ... only 20dB of noise would be considered a relatively quiet system, while a typical office environment is around 40-50dB, and comfortable hearing levels are said to be below ...