You can buy what s called a soundproof foam corner block amazon link.
Soundproofing sliding barn doors.
You can attach this acoustical foam block on the entire length of the door.
To soundproof a sliding barn door make sure there are no gaps or cracks that noise can travel through.
Get a barn door style sliding door a thick door made of solid wood is better than glass or hollow wooden doors for blocking noise.
A door sweep and weatherstripping tape can be used to cover gaps.
Attaching acoustic panels to your barn doors is another effective option.
Sliding barn doors are the easiest sliding doors to soundproof in my opinion which means that you have plenty of options to do this.
Make sure the doors are made from solid wood meaning a solid and not a hollow core.
However the down side to this option is the price.
There are two types of acoustic panels.
Therefore investing in a solid core wood door can definitely help.
Soundproofing barn door using this method is a bit of a risk.
Weatherstrip the door as you can see weatherstripping the door is very important since it s something you have to do for every door you want to soundproof in general no matter what kind of door it is.
Fiberglass panels and foam panels.
If you have a sliding barn door that looks like the one in the picture below then you will probably need a bit more than a small weather strip to stop the noise.
Else you are planning for an ugly scene.