I have severe hearing loss and tinnitus due to Ménière's Disease surprisingly, not too many loud gigs and festivals! My hearing aids have custom molds which I wear to gigs with the sound turned down low. This gives me the same protection as custom earplugs.
There is help and advice available at the festival from the Deaf Zone stall very near the Info Point near the Meeting Point/TonyBenn Tower. You can also get basic earplugs at the Info Points should you forget to take any with you. 😊