leaking sound

There are hundreds of possibilities. I'd check the toilet first though. That is the easiest to check and often it will overflow in the tank or the stopper goes bad.

Close the shutoffs for all toilets to see if the noise stops.

Check your outside spigots.

Our basement flooded when one of the kids opened an outside spigot in January and nothing came out 'cuz it was frozen. He left it open and a mid-winter warm spell allowed it to thaw out. It came on full blast and since the ground was still frozen and covered in snow, the water found a path under our back door and into the house.

Luckily my wife was running late that morning and was home when it happened. Otherwise it would have been an all day event.

Look into the bowl. A leaky flapper; when you hear this noise, will shimmer water in the bowl. Clean or replace the flapper, if needed.

Can also put that blue stuff in the tank and see if it shows up in the bowl.

Aspasia