Earplugs or earmuffs?
Both offer adequate hearing protection; the key is selecting a protector that's comfortable and convenient so you'll actually use it.
Disposable foam earplugs that you twist, then let expand into your ear, are the very best because they block the ear canal completely. They're cheap, unobtrusive and lightweight. But I personally can't get used to these; they feel like insulation stuffed into my ears. And they're so effective that they make me feel disconnected from my surroundings. I need to hear some of the whine of the router and whir of the circular saw to know that I'm not forcing or binding the tool. Jaw movement can dislodge them, they're tough to use when you have an earache and, of course, you need to remember to replenish your supply. But if your ears are very sensitive and the feel doesn't bug you, these might be right for you.
Earmuffs generally don't block quite as much noise, some people consider them hot and clunky, and if you have glasses or long hair they may not seal completely—but I'm partial to them. They offer adequate protection, and wearing them is second nature now. (When they're not in use, I automatically prop mine up and out of the way atop my head like Mickey Mouse ears.) They serve as ear warmers in chilly weather, and more than once they've absorbed the impact of a blow that would otherwise have been absorbed by my noggin.
Reusable molded earplugs, often on a cord or headband, offer the least protection of the group. But they're lightweight and cheap, so it's convenient to keep a couple of extra pairs around. And even if they're not the best performers, they're adequate for most situations. Hearing protectors have a noise reduction rating (NRR) printed on the package. Noise is measured in decibels (dB); each 10 dB jump reflects a doubling of the noise level. The idea is to get the noise reduced to a safe and comfortable level; for a two-hour stint in your workshop, that should be less than 90 dB. Foam plugs offer an NRR of about 30 dB; earmuffs about 25 dB; molded plugs slightly less than 25 dB. For extremely loud operations, wear both plugs and muffs to attain an NRR of 35 db or more.
Common Sound Levels
Normal conversation . . . . . . . 60 dB
Shop vacuum, table saw . . . . 95 dB
Belt sander, jigsaw . . . . . . . . 100 dB
Router, circular saw . . . . . . . 110 dB
Chain saw, nail gun . . . . . . . . 120 dB
Jet engine, pain threshold . . 140 dB
The 30,000 tiny hair cells arranged in our inner ear's snail-shaped cochlea are responsible for transmitting sound. The hairs nearest the opening are responsible for transmitting high-frequency noises and are the first ones damaged by loud noise. That's why people with hearing damage can hear a low-pitched male voice with better clarity than a higher-pitched female voice.