I recently went on a business trip to Stuttgart and had an early flight home on the next day, so I stayed at the Mövenpick Hotel Stuttgart Messe, which is in walking distance of the airport. My room had an extra connection door that lead to the room next door. On the last evening I was able to capture a couple next door by putting my smartphone under the gap of the connection door. The recording is a bit muffled, nevertheless her moans are quite clear. At 11:40 she says "So viel (unverständlich) habe ich nicht mehr gehabt/I haven't had this much (inaudible)", therefore I assume that they were Germans.