Does it have shutoff valves? You must have used them when you replaced the washers. Dis the noise go away then?
Where are the fawcets? Attached to the wall, or attached to the tubs? I suspect they are wall attached. The seats for the washers are sometimes just the end of a tube rolled over inside the faucet assembly. If these are worn, cracked or loose, the water will leak out of the assembly and into your wall.
As soon as you are able, shut the water off and remove the faucet assembly from the wall. Or quicker still, look below the tubs for the lost water. If it goes on very long, it means drywall replacement. In worst case, it is a place for mold to grow.
My late business partner and wife bought a house in Bend, Oregon. They were the second owners. The house was a split level with the garage in the basement. When all was quite, as they were moving boxes into the garage, they hear similar noise and upon investigation, discovered a leaking laundry faucet. All the drywall had to be removed, along with some studs. The leak had been there since the house was built and the first owner didn't know it.
No, I shut the pressure off at the meter (main entry to the house). It's the *hot* water BTW, I can feel a bit of steam, but no liquid comes out.
It's one of those plastic laundry tubs with the faucets attached to the back of it-- set into a wood cabinet with doors.
No water, just a bit of steam and hissing is evident. Everything under the sink is dry.
I don't see any leakage-- this has been going on for some time. There's unfinished basement directly below, so I think I'd notice any kind of a serious dripping really fast.
Now this is the weird thing- there's a thin (maybe 1/4" diameter) white plastic tube that runs down from between the two taps (which I can just see if I get my head under there). It's *hot*. So it's some kind of leak protection that is literally p*ssing money down the drain?