You can’t. It’s almost impossible for the average person to soundproof a dog crate against low-frequency noises like thunder, or even against most higher frequency noises. Here’s why.
- Soundproofing is bulky, so you need lots of space. You essentially need to build a room around the crate. A room with walls thicker than the exterior walls of your house.
- The necessary materials are specialized, expensive, and heavy.
- You need to be willing to give up the portability of the crate.
- And even if you can do all this, you can’t soundproof it against low frequencies (e.g. thunder, fireworks displays). And this is generally the reason why people try to do it in the first place.