I've noticed this for YEARS and I've always wondered about it. In certain films, soaps and dramas whenever there is a baby crying in the background there is a certain cry that is EXACTLY the same, it has to be the same recording used by literally everyone in the producing universe! It's definitely the same sound... like a low moan and then a high one. I've noticed it probably 50 times on loads of different things but frustratingly the only thing at the moment I can remember is when baby Tyler is crying in his pram on the "Jolly Boys Outing" Only Fools episode... now tonight I'm watching Lion on Netflix and at 1:42:48 it happens again.
I cannot be the only person who has noticed this!