Choppy Audio with Plantronics USB headset after software update
This was a problem with MacOS Sierra 10.12.4. It was fixed in the latest update to MacOS Sierra 10.12.5, which was released today (May 15, 2017). Update to the latest release of MacOS!
From the release notes:

This update:

Fixes an issue where audio may stutter when played through USB headphones.

Enhances compatibility of the Mac App Store with future software updates.

Adds support for media-free installation of Windows 10 Creators Update using Boot Camp.

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