  In the present work we theoretically analyze the effect of the Fermi surface
local geometry on quantum oscillations in the velocity of an acoustic wave
travelling in metal across a strong magnetic field. We show that local
flattenings of the Fermi surface could cause significant amplification of
quantum oscillations. This occurs due to enhancement of commensurability
oscillations modulating the quantum oscillations in the electron density of
states on the Fermi surface. The amplification in the quantum oscillations
could be revealed at fitting directions of the magnetic field.
