  In recent years, it has been shown that the phonon dynamics may serve as an
indirect probe of fractionalization of spin degrees of freedom. Here we propose
that the sound attenuation measurements allows for the characterization and
identification of the Kitaev quantum spin liquid on the hyperhoneycomb lattice,
which is particularly interesting since the strong Kitaev interaction was
observed in the the hyperhoneycomb magnet $\beta$-Li$_2$IrO$_3$. To this end we
consider the low-temperature scattering between acoustic phonons and gapless
Majorana fermions with nodal-line band structure. We find that the sound
attenuation has a characteristic angular dependence, which is explicitly shown
for the high-symmetry planes at temperatures below the flux gap energy.
