A student recently asked me about wearing ear plugs while piping. My advice: YES!
Pipes are loud. Hearing damage is cumulative. It might be okay to be around loud pipes for a few minutes a day, but if you are practicing for longer sessions or playing in a pipe band, you'll definitely want to reduce the amount of sound hitting your ear drums.
Pipers used to argue that earplugs muffle or distort the sound, making it hard to tune the pipes or hear the playing. This is true with the cheap foam earplugs.
Today, there are a couple of great options that offer hearing protection specifically for musicians. They are based on the concept of flat attenuation, i.e., they reduce the sound equally across the whole spectrum of sound. This means you hear everything, just a bit quieter. Perfect!
Option #1 (less expensive):
High Fidelity Hearos
These great earplugs are a great price (~$15 USD) and provide 20 dB sound reduction. You can buy them online and one size fits all.
Buy them online.
Option #2 (more expensive):
Custom Fitted Musician's Earplugs
These great earplugs are more expensive (~$150-200 USD) and you can choose you level of sound reduction. These earplugs are custom fitted to your ears. You need to find a place that offers this product, I recommend you call around or search online for places that make hearing aids, etc. The professional takes molds of your ears and then the molds are sent off to a lab where they make your custom earplugs. I have had these type of plugs for several years and I love them. They work great (I use a 15 dB or 25 dB filter). They are comfortable (I wear them several hours a day while playing and teaching).
Visit Etymotic Research for more info.
To sum up: Yes you need hearing protection! Cheap foam earplugs block the sound, but if you are going to be playing pipes for a long time, you'll enjoy the sound much more with some earplugs designed for musicians!
