Happens to me as well Also in youtube 240p quality, not in higher, so I think might be the "bad sample rate frequency conversion" as in comment #8.
Flash 64bit version 10.2 d161
$ lspci -vs 1b 00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03) Subsystem: Lenovo Device 20f2 Flags: bus master, fast devsel, latency 0, IRQ 50 Memory at fc020000 (64-bit, non-prefetchable) [size=16K] Capabilities: <access denied> Kernel driver in use: HDA Intel Kernel modules: snd-hda-intel
Happens to me as well
Also in youtube 240p quality, not in higher, so I think might be the "bad sample rate frequency conversion" as in comment #8.
Flash 64bit version 10.2 d161
$ lspci -vs 1b
00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03)
Subsystem: Lenovo Device 20f2
Flags: bus master, fast devsel, latency 0, IRQ 50
Memory at fc020000 (64-bit, non-prefetchable) [size=16K]
Capabilities: <access denied>
Kernel driver in use: HDA Intel
Kernel modules: snd-hda-intel