  The chiral anomaly is a phenomenon characteristic of Weyl fermions, which has
condensed matter realizations in Weyl semimetals. Efforts to observe smoking
gun signatures of the chiral anomaly in Weyl semimetals have mostly focused on
a negative longitudinal magnetoresistance in electronic transport.
Unfortunately, disentangling the chiral anomaly contribution in transport or
optical measurements has proven non-trivial. Recent works have proposed an
alternative approach of probing pseudoscalar phonon dynamics for signatures of
the chiral anomaly in non-mirror-symmetric crystals. Here, we show that such
phonon signatures can be extended to scalar phonon modes and mirror-symmetric
crystals, broadening the pool of candidate materials. We show that the presence
of the background magnetic field can break mirror symmetry strongly enough to
yield observable signatures of the chiral anomaly even in mirror-symmetric
materials. Specifically for mirror-symmetric Weyl semimetals such as TaAs and
NbAs, including the Zeeman interaction at $B \approx 10$T, we predict an IR
reflectivity peak will develop with an $\mathbf{E}_\text{IR}\cdot\mathbf{B}$
dependence.
