According to the article,
Thief v1.33 and Thief 2 works with DS3D, so there is no need to use the A3D.dll file for this game.
Unless you insist on playing the original, unpatched game, then there is one other reason Thief isn't allowing the use of Hardware Audio. You cannot turn on Hardware Audio
after starting a mission, so make sure you go to the Audio Options as soon as you get the Thief menu.
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