These are your basic earplugs, available from chemists and usually less than $2 a pair. This packet's looking a bit scruffy because it's been floating around in the bottom of my handbag for a while. When you unwrap them, they look like this:
They're two small cylinders of foam, roughly the size of the top joint of my little finger. The foam's very soft and has lots of tiny air pockets, which means it shrinks and deforms when you squeeze it, and then once the pressure is removed it slowly returns to its original shape. This is the key to its success: you squeeze them down in to little thin things, like this:
|This one had already started expanding again by the time I took the photo|
They don't block out all sound, they just dull background noise from a roar to a murmur, and take the edge off very loud or sharp sounds. You can still hear people talking directly to you while you're wearing them, and other essential sounds like warning sirens get through as well.
I could not go grocery shopping without these babies. They're fantastic for dulling the shrieking children, squeaking wheels, humming lights and general aural chaos of shopping centres. I also use them for loud concerts and events - I don't think I'd have survived Top Gear Live without them!
On the downside, they do make your own internal noises much louder. While I was shopping my footsteps echoed through my body, and when I started tapping my teeth in time to the song stuck in my head (which is just a thing I do) that was really loud as well. Talking with them in sounds very odd indeed, and eating with them is fairly well impossible unless you really like chomping, smacking noises.
They're really, really useful things to have, and I always keep a couple of pair in my handbag along with the rest of my emergency supplies: band aids, anti-tummy-bug pills, travel sickness pills, and hopefully paracetamol if I ever remember to restock those.
When I had long hair (or if I'm wearing a long wig) I can bring my hair forwards so it covers my ears and the earplugs aren't even visible. But I usually don't bother: it hurts nobody that I wear them, and the reasons why are nobody's business but mine. I don't care about looking normal. I care about being comfortable and getting stuff done.