Affects Version/s: Minecraft 1.4.5, Minecraft 1.4.7, Snapshot 13w04a, Snapshot 13w05b, Minecraft 1.5, Snapshot 13w11a, Minecraft 1.5.1
Fix Version/s: None
Environment:Windows 7 X64, latest JAVA JRE7 x64 (as of Dec 7 2012 from Oracle). Unmodified Java, Unmodified Game. Dell Vostro 220 PC Dual core, with onboard sound. Drivers up to date. Machine not under heavy load when problem presents. Using Shift F3 screen to view sound usage.
Problem presents and is easily reproducable when near a large number of animals (player made farm). in our case 20+ chickens, 10+ cows, 10+ pigs in a 64block square area.
When out in a "quiet" area, sound runs at about 0.2% - 0.5% on the Shift F3 Menu pie chart. When near the animals, this jumps to 7% - 10%. When it spikes, it results in a sudden FPS drop to 0-5FPS which lasts for about 5-10 seconds at a time, and occurs anywhere from every 30seconds to every couple minutes.
If sound is turned to 0% in the settings, the usage drops to 0.1% and the problem is no longer reproducable (but we have no sound)
Another user reported the same problem here, with the exact same symptoms (and screenshots): http://www.minecraftforum.net/topic/1558241-major-fps-drop-due-to-sound-with-14/
Also another user reported the problem in this thread: http://www.minecraftforum.net/topic/1403906-131-fps-issues/page__st__20 (post number 36 by user HeroUnit23)
This does not happen on our other computers, only that one computer, though the OS/settings are identical. We have reinstalled to no effect.
We noticed the problem when we built the new animal farm. So we just killed all the animals and the issue was no longer a problem. Also if we leave the vicinity of the farm the problem doesn't occur.
Hopefully you can track this one down and solve it, it's a HUGE annoyance.