How do I stop sound interruptions of 1 to 2 seconds throughout an entire YouTube video?

Windows XP, Professional Version 2002, Service Pack 3. Firefox 45 and Shockwave Flash 20. Search engine is Google.

The problem is that audio in YouTube videos has many 1 to 2 second interruptions throughout the video and some are longer in length. They are frequent enough to be too annoying to watch and listen to the video.

Any sound played through Windows Media Player works fine. This issue so far is entirely with sound coming from YouTube videos.

I have upgraded Firefox to it's most recent version which is supposed to address this type of problem and I have uninstalled and reinstalled Shockwave Flash with no noticeable improvement.

Operating Firefox in "Safe Mode" showed no improvement.

Any advice you can give me to resolve this issue would be appreciated.