Loading an asset from an Asset Bundle without a file extention

I'm using asset bundles to load localised VO. These VO files could be .wavs or .oggs and it's not viable to specify which before loading the file. This is fine when loading the default files from Resources since Unity doesn't require the file extension. However when loading the localised files from an Asset Bundle, if the file extension isn't included in the load call the file can't be found. The manifest file does include the extension.

Is there a way to load a file from an Asset Bundle without providing the extension? From what I hear, this was doable in Unity 4 but I'm having the problem using Unity 5 (5.1.2p3).