I was in a similar situation a year ago when I lived in an apartment. I tried asking nicely but it continued. I got so annoyed from lack of sleep as it was every night for weeks that I finally lost it. I wrote a giant note on their door for any who passed to see explaining my frustration with the nat geo type noises that were keeping me up. I wrote a preferred time 7am to midnight that I wouldn't mind and asked them to keep it down at all other hours. I then proceeded to tell a few other tenants about the occurrences, no surprise they had heard them too, and word spread quickly. The couple seemed slightly angry with me at first but later apologized and kept it down for the most part
