The graph shows the attenuation by atmospheric absorption as a function of frequency, temperature, relative humidity and distance. It is advisable to compensate for this loss in a certain percentage, but never apply a 100% compensation since high frequency drivers might be damaged. This compensation is recommended for the units on top of line array systems (those aimed at the distance introduced) or for sound reinforcement systems installed outdoors, where intelligibility is a requirement and large distances have to be reached. This attenuation is different from the 6dB loss per doubling of distance typical of spherical waves.