So, where are audio devices file in OSX?
According to the Mac OS X Developer Library:
The Audio family does not export device interfaces for applications to access audio hardware directly. However, it does provide a device interface that the Audio Hardware Abstraction Layer (Audio HAL) uses to access drivers derived from the Audio family.
So I guess you need to find more information on "Audio HAL"
Here are some suggestions.
If you are talking about Hardware Abstraction Layer (HAL) devices, then the path is
By default there is one bundle there: on my Mac
Other devices may use Kernel Extensions; bundles that end in