According to the fit we get a gradient equal
to 4.13, which is close enough to equation (12c).
R 0.975 indicates the validity of the fit and
reinforces equation (12c). The dispersion of data
around the trend line can be explained by the inaccuracy
of the manual measurements of the sound
intensity and anisotropic background noise. For
better accuracy, as mentioned, the experiment
should take place in an acoustic laboratory.