  Recent experiment demonstrates magnon to phonon conversion in a YIG film
under the application of a non-uniform magnetic field. Light scattered from
phonons is observed to change its polarization state interpreted by the authors
signifying phonon spin. In this note we argue that the experimental data merely
shows the exchange of angular momentum $\pm \hbar$ per photon. We suggest that
it has physical origin in the orbital angular momentum of phonons. The
distinction between spin and orbital parts of the total angular momentum, and
between phonons and photons with added emphasis on their polarizations is
explained. The main conclusion of the present note is that phonon spin
hypothesis is unphysical.
