Audio "Popping" Noise Upon Export

Hello!

I create Walt Disney World videos for YouTube, and lately I have been noticing "popping" sounds in my audio. This popping sound only occurs in the exported file. The audio I am using in these videos does not have these popping noises and the files range from .mp3 to .aiff. The audio sounds fine until I export, so the problem must be occurring there.

I am using the latest version of Final Cut Pro, 10.2.1. I have tried uninstalling and re-installing Final Cut as well. I am editing on the 13" MacBook Pro Retina Late 2013 Release with a 2.4 GHz Intel Core i5 processor, 8 GB 1600 MHz DDR3 memory, and Intel Iris 1536 MB. I have my Libraries located on a 500GB USB 3.0 WD Passport.

I have uploaded an example video of the "popping" audio that persists on my exported video files: https://vimeo.com/131829811

The audio used in that example clip is from the YouTube Audio Library and is an mp3 file. It sounded fine in FCP, this popping appeared after exporting as a Master File with Computer Format, H.264 Better Quality, 1920 x 1080 Res, 48 kHz Stereo, & Quicktime Movie AAC Audio File Format (the root of the problem).

My Project Settings are always 1080p 59.94p Stereo 192kHz Apple ProRes422.

I have been experimenting all day and find that when I export audio only using any audio file format other than Quicktime Movie AAC this problem does not persist. If I were to export a video and then export the audio separately using Export File> Settings> Audio file format> AIFF and then combine them in iMovie and upload that to YouTube, I could work around the popping problem.

I would rather like to figure out a way to export the Master File with an audio file format other than AAC. Is this possible? The AAC export format is what is causing these popping noises, but is there a way to export a video in another audio format without having to export the audio separately? Or a way to change the 48 kHz export quality? Thanks for any feedback!