dsound.dll
This file is not a system component: windows itself, not a download. Restore it from the source that installed it rather than downloading a replacement.
Do not download this DLL on its own
Searching for a missing DLL by name leads to sites that hand you that single file. It is one of the oldest and most effective malware delivery methods there is, and a system DLL from an unknown source is indistinguishable from a deliberately modified one. There is never a legitimate reason to obtain a runtime component that way.
What it is
The DirectSound audio library, part of Windows since the DirectX 9 era. Like d3d9.dll, it is a system component rather than something publishers redistribute.
Where you see it: Old games, and very commonly after installing an audio wrapper or mod that dropped its own dsound.dll into the game folder.
Check the game directory first. If there is a dsound.dll sitting next to the executable, it was put there by a mod or wrapper and is the actual problem: remove it and see whether the game starts. If the error persists, the DirectX End-User Runtime supplies the legacy audio components.
Why there is nothing to download here
There is no verified download we can offer for this one, because installing a file is not the fix. The steps above are what actually resolves it. That distinction matters: the sites ranking for this file name are selling a download that would not have helped even if it were safe.