How to soundproof partial wall?

At my work, we share a wall with another company. It is a retail store and very loud. Our office is a more professional office setting; so the noises are very distracting. There’s roughly a 4’ tall by 32’ wide opening on top of the partial wall that separates the companies. Does anyone have any ideas on how to “soundproof” this opening? For code reasons, we can’t extend the wall up. It also doesn’t need too 100% soundproof it, just something there to dampen noises. My first thought was a curtain, but a 30’ unsupported rod seems very unlikely..