You, from the khanacademy staff can evaluate the sounds and then (if the sounds seem appropriate) let the program be published.
Ah! And i am in favor
(YES!)

Also be great learn how to add sound effects to games!

Adding WebAudio oscillators (sine/square wave tones) might be an option.

I think we should add sound to programs to teach people about sound in programs.

A small problem:
Real Javascript doesn't have that sort of function.
So, I guess I'm saying
NO

I'm not able to upvote for some reason (browser hangs), so I'll leave a comment. This would be a great feature. It would also open up the possibility for audio processing, which can illustrate amazing CS principles like filtering... and relate them to graphical filtering and data filtering. And it would make games more fun :)

I would love this feature. As is, programs in Khan Academy are lifeless pixels. Adding sound could add a whole new dimension to program flexibility.

It would be great if we could choose from a variety of instruments from 64-bit to violin and a selection of notes that play for about a second to add to the program. But I do realize that playing a single (likely high) note repetitively may also count as annoying in some instruments. KA should also have a handy volume controller at the bottom next to save spin-off.

I saw some concerns about standard programming not needing sound. How about if we get a separate mission for that one? That would keep the current coding missions more-or-less as they are but would also allow some umm.... 'bells and whistles', so to speak.

i have an idea!
maybe like how there is a project evaluations place, there could be a project publish place and the people could revise the program and check if it is appropriate to post.
if there is sound in the program they could revise that to.
That way there wouldn't be any more cases of the screaming sound (credit to Mm Milad for that quote) and people could have sounds in there program!

You could use a var example = getSound () command like you do for images. Good sounds could be:
"Oh Noes!"
Laser
Swish
walking
cartoon falling
thud
Low, Middle and High tone octaves
error
Record and have Aproved

This is now available: https://www.khanacademy.org/computer-programming/what-does-oh-noes-say/5306255674179584
More sounds will be added in the coming weeks.

There is sound available this is how you use it
playSound(getSound("rpg/battle-magic"))

I would love for there to be a command to alter the pitch of sounds.

It could lead for some more variety of projects, and it could influence more users to incorporate sounds in them.