How do I listen to a kiai on the market before I buy it? Sorry if it's really obvious, I just can't figure it out.

When you buy a kiai item, you buy the slot where to upload a file audio that you choose. You can change it whenever you want.

I mean the ones for sale by other players

It's the same thing. You buy only the slot, it's like textures.

There are some kiai makers, but they don't sell you the Kiai Item, is this what you mean?

I think so, let me give you better context, I bought a kiai from the official store and uploaded my sound, I then made it for sale at 2000tc, someone bought it from me so I assumed they liked my sound, now I bought another one and made it for sale, but when I viewed it in the market I couldnt figure out how to listen to it.

Actually the Kiai's value is 2k on the market, so the guy bought it from you because it had the right price. The sound wasn't important. You can't listen them, your aim when you buy a Kiai is to upload your own sound into it. Just remember that the file has to be a .wav and it can't be longer than 5sec.

I belive you have to just get lucky if people sell it with a sound or not

Price doesn't factor whether or not the song is on the item. From my knowledge You can't even listen to an attached piece on the kiai item thats listed the market by choice (I even went and checked again).

If you think you're good at making kiais, why not try make a shop, In the art thread and selling them?
You don't need to have the item to sell the noise btw.

http://forum.toribash.com/showthread.php?t=439019 Theres an example of a kiai store. :L