In chap. 3 of "Fractal Geometry of Nature" Mandelbrot mentions that "part of the study of fractals is the geometric face of harmonic analysis" (spectral or Fourier, he specifies). But to my dismay this is immediately followed by "...but this fact is not stressed in the present work."
Google hasn't turned anything up. Can anyone here orient me on how fractals and harmonic analysis are related?