Chopping audio usually is the results of 2 things...
1)faulty hardware acceleration support for flash player. If that is the case just disable it as indicated above.
2) aggressive cpu power throttling. To diagnose that:
sudo apt-get install cpufreq-utils
sudo cpufreq-selector -g performance (this will change the cpu throttling governor from "ondemand" to performance.
Now check to see if your problem is fixed.
Also... cranking up the sound quality settings in pulse audio might also help:
sudo nano /etc/pulse/daemon.conf
Scroll down where it says default-sample-rate and change it to 48000 (dont forget to remove the semi-colon !! )
Also if you have a relatively good cpu you can improve the audio quality a little more by moving a few lines up, to the "resample-method" line and change the speex-float number to 5 .
Ctrl+o and ctrl+x to save and exit. Restart pulse audio or the whole system for the settings to kick in.