Firefox11
音が出るタイミング（wasdで移動など）でエラー
動作が完全に止まる
--
[12:45:23.569] uncaught exception: [Exception...
"An attempt was made to use an object that is not, or is no longer, usable" code: "11"
nsresult: "0x8053000b (NS_ERROR_DOM_INVALID_STATE_ERR)"
location: "... /exploit/sound.js Line: 36"]

oggしか対応してないから当然っちゃ当然だが
両対応出来るようにしといたほうがいいよ