I will agree with; emphasize; and expand upon what a few others here have said:
1. If you are playing in a live band that rehearses in nearly any room with amps and a drummer (i.e., not headphone/IEM rehearsals), you need hearing protection, no question about it;
2. Forget the meters; it's a function of time, i.e., length of exposure. Sure, a really loud (120db or more, like a nearby thunderclap or gunshot from a pistol on the smaller side) but short sound can damage your hearing much more quickly than the same sound at a lower volume, but long-term exposure to even 75db (like a running lawn gas-powered lawnmower) of sound pressure can damage the nerves that comprise part of our hearing system. Noise is considered one of the most common occupational hazards of modern times, and that's just in general; think about about what that means for musicians.
I've been a professional musician (both touring and studio work/production/etc) for nearly 20 years, and I've used Westone custom earplugs the entire time. I can't recommend them enough. It'll cost ya, but they are worth every penny: my ears get sore from those cheapo foam earplugs meant for construction sites, and the foam cuts out way too much audio information. The Westone earplugs are a perfect fit; I can sleep with them in. Used to do it in the tour bus all the time. The filters they use are attenuated such that it's just like turning down the volume: it's an even cut across the frequency spectrum. The only drawback is the filters are pricey and are damaged or destroyed by moisture. I sweat like a whore in church when I play onstage, so when I was touring a lot, I went through a lot of filters. Thank you, sponsorship. 
I know guys who are so protective of their ears, they wear earplugs when walking down the street in cities like Chicago or New York; they claim the sound of bus air brake systems damages their hearing. And if you're standing next to the drummer (especially on the ride side of the kit), that's a lot of potential hearing damage to protect yer ears from, mate. (And yes: I would say the sound of clanking/clattering shopping carts will definitely damage your hearing at certain frequencies over time.)
Have you ever heard a persistent ringing or high buzzing/whining in your ears that goes away after a short time? That's the last time you'll ever hear that specific frequency: it's the sound of that nerve dying. Those nerves rarely grow back, and if they do, it's at a snail's pace. That's how tinnitus starts.
So don't wait: use foam earplugs until you can get yer ears fitted for a proper pair of earplugs, and then protect them once you gots 'em.
Hope that helps.
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