Yes it should be. The audio .rsc files are included in the resource of the mod kit, so I assume it would be a case of putting together a .wav file (that is what the vanilla ones refer to), giving it a .rsc, then finding something to trigger it, a building or event.]
The only thing I don't know how to do is find a place to trigger the sound. Not sure where that is coded in.
Attached is the blacksmith audio rsc.
<a class="ipsAttachLink" href="<___base_url___>/applications/core/interface/file/attachment.php?id=890" data-fileid="890">Blacksmith.rsc</a>