Logarithmically-spaced Dirac comb
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Like the standard Dirac comb, the logarithmically-spaced Dirac comb consists of an infinite sequence of Dirac delta functions. In the case of the logarithmically-spaced comb, these are spaced in octave intervals, i.e., the delta functions are placed at positions 2kf0, for all integers k.
In musical applications, this type of Dirac comb can be used to create a 12-note scale that spans the infinite space of octaves. Such a log-spaced Dirac comb, with perhaps a Gaussian weighting, when ascending or descending, gives the well known Shepard tones effect of a sound which is perceived as though it is forever going up or down in pitch.
