Is it possible to have a non-whole number harmonic in sound?
By definition: Harmonics, are frequencies which are integral multiples of the fundamental (including the fundamental which is 1 times itself).
It need to be appreciated that non-whole numbers are not integers.
We also know that any frequency which is greater than the fundamental frequency of a sound is called overtone. In Fourier analysis of a signal, the fundamental and its overtones together are called partials. Fourier analysis provides for the inclusion of inharmonic partials, which are partials whose frequencies are not integral multiple of the fundamental. But these are not harmonics or harmonic partials.