There are some known sound bugs in the current Flash Player release, although your problem sounds quite different.
That known problem will be fixed in the new Flash Player that will be released later this week. Or you could try the latest Flash Player 11.8 beta: http://labs.adobe.com/downloads/flashplayer.html
Some audience members connecting to my Adobe Connect sessions have the same kind of problem. Did the update fix it?
Thank you for following up.
Unfortunately the Flash Player 11.8 beta made no difference.
I tried it on youtube and perversely the ad at the beginning was loud and
clear but the actual video sound was inaudible!
Last night I read of a similar headphone issue at https://code.google.com/p/chromium/issues/detail?id=169846 experienced by users of Google Chrome.
Looking at the linked bug report, they've been working on it for months, and issued another fix in the latest development release, which you can get at https://www.google.com/intl/en/chrome/browser/index.html?extra=devchannel#eula. I'd be curious to know if it fixes your problem. Google more tightly integrated flash with chrome, so their fix might work even when other browsers still have problems.
Sorry to bump an old post but I've got a very similar issue.
I have updated flash player and Chrome. I also have Firefox and IE installed and the issue is the same in all browsers. The Volume mixer is all the way up.
Sound plays fine through my speakers.
I plug in my earbuds and everything plays without issue.
I plug in a pair of Califone CA-2 headphones and suddenly there's no flash volume (or maybe like 1% because I can VERY faintly hear something). I can hear system sounds. I can hear mp3s playing through foobar. But no Flash sound.
If I plug in the earbuds, suddenly the sound is back.
This is such a bizarre issue. Any ideas? I tried google but couldn't find anything.
I'd appreciate any help the community could offer.