Phonons are lattice vibrations. The distance between two consecutive phonons is of the order of $1/N$  where $N$ is the number of atoms in the lattice. At room temperature a phonon travels approx 10 to 100 lattice constants before scattering. 

In [this article](https://doi.org/10.1038/srep17131)
they say that a phonon travels $< 1 \mu m$ before scattering, that is approx 100 lattice constants (the lattice constant is approx 1 nm)