The funny thing is that I rarely wear ear plugs when I play on stage, but I almost always wear them when I'm sitting in the audience. Ususally when I'm on stage, the sound is projecting away from me and the monitor speakers usually don't get loud enough to cause that distortion sensation. But if I'm sitting anywhere near the club's PA speakers, that sound just drives my ears crazy and I have to wear ear plugs; otherwise, I'll hear that distorted sound several days afterward. The sound is similar to the sound a speaker makes when it is overdriven. It's extremely annoying and something I wish I would have taken measures to prevent when I was young and stupid.