New one on me, and very strange. And you're right, that's spooky.
So, even if the basic freq is above your audio range, the amplitude of the steam-scream "deafens" you to all other sounds? That really is strange!
Thanx for posting. Filing under "things I never knew".
That's what we were told in Fire Fighting School and by ones on ship who trained us in Damage Control. Even when the boilers are shut down you'll still should hear some operational noises like fire pumps etc. If you don't hear anything you have Big Trouble. When they are operational you'll hear loud operational noises requiring hearing protection.