First for a quick overview of supported codecs in browsers...http://en.wikipedia.org/wiki/HTML5_audio
Secondly it's important that you understand that Microsoft politically polarizes everything for their corporate gain. Even if Internet Explorer was actually the most standards compliant browser it's still important to make it clear you don't use the big blue E for browsing the web, ever. They are part of the MPEG-LA patent pool (patent trolls) who are trying to push the license burdenered H.264 codec down everyone's throats so they can charge people for the format, thus they along with Apple (Safari browser) intentionally to not support free and thus standard codecs. They use the lame excuse of "works if the user installs the codec" as an excuse to suggest they are open to competition however it only emphasizes their anti-competitive intentions. Additionally both
the W3 and WHATWG have refused to enforce an open codecs policy so it's important to remember that we web designers and web developers ultimately set the trend for what becomes standard when even the standards bodies fail to live up to the definition of an institution.
Lastly you're going to have to determine the browser support and then serve the best codec version of the sound you wish to play. Make sure that if you find it necessary to support license burdened codecs that you detect them after
you detect support for standard/open codecs.