The sound level can be measured but no precise
indication exists for the range of the sound. Too
many unknown factors affect this value: type of
sound, speed and direction of the wind, humidity,
fog, rain etc. etc. The data shown in the following
table are useful as theoretical indication.
The intensity of a signal is always respective -
see table on the right.
An increase in sound of 3 dB is heard as a
double sound level.
