Sounds can be set to play whenever events happen in your chat – new PM, your-nick-mentioned and so on – you can choose what these are in prefs. Of course, supporting sound in all browsers has sometimes been tricky but now, depending on your browser capability, Mibbit plays .ogg and .m4a sounds in addition to Wav and Mp3.
To use your own sounds pick an audio file in the right format for your browser and upload it to the web. Next, enter the reference to the file into Prefs replacing the standard Mibbit one. Save and Close and you’re done, the new sound will be played each time the event happens.
For Widgets, where visitors have many different browser types, you might wish to upload several different audio formats of the same sound. If you do this and remove the reference in Prefs to the file extension we will detect local browser sound playback ability automatically. This is done in the following order: .ogg > .mp3 > .m4a
We’ve found Chrome plays most things, Firefox is fine and IE will play mp3 unless you’ve upgraded to IE9 which supports more.
And if you need it you can play sounds from the command line using ‘/splay <url>’ This kind of thing is useful for putting into aliases or even with the onJoin command. 
Related posts: