Running Firefox 38 on Slackware Linux, I hear frequent painful sharp loud clicks, like an audio buffer full of garbage because a of callback not running in time

Running Firefox 38 on Slackware Linux, I hear frequent painful sharp loud clicks, like an audio buffer full of garbage because a of callback not running in time. Seems to happen when firefox hits 100% cpu usage for a moment. I guess this site is just too CPU intensive for my oldish CPU.