I think that's normal for a laundry room sink to gurgle.

Is this a new thing for the guest bathroom sink or have you always know it to do this. It sounds like a venting issue to me.

My problem is my terlet. I bought a replacement flap today hoping that what's wrong in my terlet. There is a leaking dripple noise and then a periodic water running noise of topping up the terlet tank. Wish me luck.