I don't think that those sounds are supposed to play in firefox but if they are then go to tools then options. make sure that your character coding is on unicode under view then character encoding firefox had some problems for me until I turned it to that, it might fix the problem.
view is at the top of the screen between edit and history it is visible without pulling anything down, sorry if I worded that wrong before. to be very clear view is not under tools it's not actually under anything at all.
I tried the unicode thing and still no menu pop or restore down/minimize sound however I did find a add on that enables the internet start and stop sounds which makes me think that there might be an add on for other sounds.
I actually don't use sound when using firefox so I don't even know if mine is working or not, I did have to fix my sound once though in firefox I can't remember what else I changed, if I remember I'll post it.