Here’s app note from Abracon for EMI suppression using ferrite beads. Link here (PDF)
A ferrite bead is a passive electrical component used to suppress high-frequency noise, EMI, and crosstalk in electronic circuits. They come in different shapes and sizes; some beads are available in the form of clamp-on cores, like the ones found at the ends of laptop chargers and digital signal cables. They can also be found as through-hole or SMD components, which are more suitable to be mounted on PCBs.