Discharge of some bulk solids such as hard polymer pellets or corn starch from aluminium silos generates loud honking noises and vibrations. Whereas the noise emissions re considered primarily as an environmental issue, the vibrations may have an effect on the structural integrity. The vibrations are associated with slip-stick behavior, but cannot be predicted.

Many attempts have been made to reduce the honking from silos. Results from test and full scale silo installations demonstrate that honking can be reduced by generation of a boundary layer along the silo wall. This will also change the pressure distribution within the silo.

Currently the only method to reduce vibrations is to use downcomers generating a last-in/first-out flow profile.