Sounds like a buzz and a sine wave mixed and lots of reverb. It reminds me of a flute. The truth is that a lot of these sounds are usually synthesized, it is the signature style of Massive Attack. As a result it shares a lot of similarities with the kind of simple analog sound makers used in hospital equipment. It doesn’t sound sampled to me, at least, but I could be wrong, it has a lots of things layered on top to say for sure. If anything, it reminds me of the stereotypical code blue alert used in drama shows. Though I have never encountered such a thing in real life, usually those things are communicated verbally without any sort of alarm. Hospitals actually avoid alarming or excitedly modes of operation, preferring calm and collected action.