The noise a Librarian makes when orgasming.
Usually followed by a Shhhhh and a "quiet Please"
Although this is a very rare occurrence. As the mating ritual of the librarian is very infrequent and when they do mate a orgasm is highly unlikely. Even in the male of the species.
Steve felt like he was going to explode. How much longer would he need to hold on for it was a personal best for him already.
All of a sudden he felt Betty spasm and let out a "Bookadobba Doooooooooohhhhh" followed by a Shhhhhhh and finally a "quiet please"
Steve knew it was time to let go although he was rather put off by what he had just witnessed.