I have a continuous hissing sound in the master bath sink and it seems to be coming from underneath the sink.I get the hissing sound even after shutting down both the hot and cold water supply to the sink.Whenever I start and shut-down the other adjacent sink,flush the adjacent toilet or start/shut-down the adjacent jet tub, I hear some sound in the master bath sink for a few seconds.It then reverts to its continuous hissing sound. There is no water leakage anywhere.
Also, after all the water gets drained in the sink, I hear a gurgle towards the end.
The sink is a moen faucet with 2 knobs: one for hot and another for cold water. All connections in the sink seem snug and secure. Hot and cold water are working absolutely fine.
Any help would be greatly appreciated.
Thanks,
Whiz

Peek under that sink, do you see an aav [air admittance valve]? Google studor vent