It wasn't the next room over, but the tent next to us. We went camping with our friends. The tents were no more than 4 to 5 feet apart. My wife (girl friend at the time) woke me up during the night and told me to listen. His breathing gave them away. He was breathing with every stroke. Every regular until it go faster and faster, leading to a huge breath and a long sigh afterwards. We tried very hard not letting them know that we heard everything.
The next morning her girl friend asked her in private if we had heard anything. She said she had tried to stay quiet, but he was just too loud with his breathing. My girl friend said 'Yes' but did not bring it up that weekend to embarrass her. We made sure we were quiet when we did it in our tent, just in case they were listening.