The propfan (also known as UDF or Un-Ducted Fan) was also very noisy. Extremely noisy. Imagine a propeller spinning at near jet engine speeds, and now you have some idea of how noisy it was.
I recently talked to a docent at the Paul Garber facility in Washington DC (connected with the Smithsonian Air and Space) and he said that it only met the stage three requirements if you were standing in the next county. They have the engine at their facility, it's pretty interesting.