Were they connecting rooms?

I have found that some hotels with connecting rooms, the noise carries into the other room very easily.

I stayed in a Homewood Suites that had a connecting door in an area where there was no carpet. I could hear the neighbor's phone calls clearly, like he was in the room with me.

Another time was at the Marriott Wardman Park in DC. The connecting door was right next to the bed and I could hear every word (and groan) the couple next door made.

If you are in a connecting room, placing a towel under the connecting door can sometimes keep your neighbors from hearing your calls, and vice versa.