Audio is deleted, but still exists in preview and published files.

Hello,

I am using a question/answer template with layers for correct, incorrect, etc. The response layers have audio chimes which need to be lowered for our course. The increase/decrease audio function does not work consistently (levels are arbitrarily changed whenever I've tried that tool), so I am trying to reduce the level in an external tool and add the new files to the timeline. The problem is that the audio is still audible once I've removed it from the timeline and if I add the new lowered audio, I hear two the audio twice.

I assume this has to do with the question slide coming from a master slide and the audio getting pulled in from there, but I have no idea how to remove the sound. 

Thanks.