Unless there's something about this in managed DirectX, there isn't any
managed object that will allow you to do this.  You'll have to find an
unmanaged method of doing this, and use platform invoke to execute the
method.  A good starting point is pinvoke.net.

However, if I ran a program that disabled my sound card without my explicit
permission (and good reason) I'd be pretty ticked off at the jerks who wrote
it.  Can I ask why you believe you need to do this?