That’s a linker error and there are a large number of things that can cause that so its a bit hard to debug without seeing your setup.
Most likely you’re not successfully linking to the OpenAL lib but are correctly including the include paths. In this case I’m going to guess its something related to trying to link to a 32 bit lib in 64 bit. You need to make sure you’re trying to load a compatible library.
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If you haven’t yet, you should check out tutorials on how to link to 3rd party DLLs.
It’s probably going be easier to do this with a dynamic library vs a static library, and probably even better to do it as a plugin if you can.