I live in an all-girl college dorm, which lends itself to all kinds of great stories... I was in the shower the other day, where I do most of my masturbating. The water was turned up as hot as it could go, and I was pumping my bigger vibrator in and out as fast and hard as I could, with my smaller, stronger vibe grinding on my clit. I was leaning against the wall of the shower so I didn't fall down, biting my lip to keep from moaning out loud. I had myself to the glorious point where there was no boundary between one orgasm and the next, just wave after wave after wave. Suddenly, I felt a thump through the wall I was leaning against. Then another, and another, and a soft, half-stifled moan. I had no idea who was in that shower, and it turned me on so much to not just hear, but FEEL them having sex. I must have let out an involuntary moan of my own, because they suddenly stopped, and after a few moments they shut off the water and all but ran out of the bathroom. I felt bad for interrupting their sex, but wow, was the rest of that masturbation session fun for me!