Earplugs are sold in most pharmacies. Because I teach at a college of pharmacy, I want my students to understand a particular feature of earplugs called the Noise Reduction Rating, or NRR. The NRR is a rating of the effectiveness of earplugs at decreasing the amount of sound (or noise) entering the ear. Typical values range from 12 dB to 33 dB; the ones I demonstrate in my class have a value of 29 dB.