The intensity of a sound source is described by an inverse square law only if the source is very small (a point source) and only if the waves can travel unimpeded in all directions. For an extended source or in a situation where obstacles absorb or reflect the waves, the intensity at distance r can often be expressed as I = cP_source/r^x, where c is a constant and the exponent x—which would be 2 for an ideal spherical wave—depends on the situation. In one such situation, you use a sound meter to measure the sound intensity level at different distances from a source, acquiring the data in the table. Use the best-fit line of an appropriate graph to determine the exponent x that characterizes this sound source.

Distance (m)     Intensity level (dB)
1 ..........................................100
3 ............................................93
10 ..........................................85
30 ..........................................78
100 ........................................70