Banshees and earmuffs

Last week I came accross a person who calls himself a Slayer Master in Burthorpe. He agreed to help me to become a better slayer. He does this by giving tasks and providing advice. He sent me to slay banshees and gave me a set of earmuffs to protect myself from their shrieks which are rumored to render a fighter incapable of concentrating on fighting...

I also saw a face mask and a bag of salt in the masters' equipment. I wonder what they are for?