What is the random alarm sound that I hear coming from TMH all the time? (I’m curious not annoyed)

I live nearby. It makes an awooooga sound for about 15-20 seconds and then shuts off. It’s never at a “round” time of day- ex. It will go off at 11:23, not 11:30. It never lasts long enough for me to record. It happens at all hours of the day/night.

It doesn’t happen in conjunction with helicopters or ambulances.