Audio pops in video when compressed. Why?

I'm getting pops in the audio when I compress my videos through Compressor 4.2. The pops are not present in Final Cut, nor are they present when I "Share Master File" straight from Final Cut. The pops only show up after the video has been run through Compressor. And it doesn't seem to be because of any clipping in the audio, because it doesn't matter if it's loud or quiet.

Here's a snipit so you can hear what it sounds like.

https://vimeo.com/138107877

Any help is greatly appreciated.

My settings are as follows. (These settings are Vimeo specified)

QuickTime Movie

Estimated file size: 2.45 GB/hour of source

1280 x 720 px | 29.97 fps

Stereo (L R) | 44.10 kHz

Specifics:

AUDIO

Channel layout: Stereo (L R)

Sample rate: 44.1 kHz (the only option available to me. Vimeo wanted 48 kHz)

QuickTime settings:

Format: AAC

Channels: Stereo (L R)

Rate: 44.100 kHz

Render Settings:

Quality: Best

MPEG-4 AAC Encoder Settings:

Encoding Strategy: Constant Bit Rate

Taget Bit Rate: 320 kbps

VIDEO

Frame rate: 29.97 fps

QuickTime Settings:

Compression Type: H.264

Key Frames: Automatic

Data Rate: Restrict to 5000 kbits/sec

Optimized for: Download

Compressor Quality: High

Encoding: Best quality (multi-pass)

H.264 profile: High

Entropy mode: CABAC