"The sound of animals is a little noisy."
DL rejected that word when I wrote it the first time, probably because they haven't introduced it in their lessons, I suppose. But yes, it's more common with うるさい。少し is not wrong but you will rarely hear this phrase in Japan. The discussion about politeness is sort of a non-sequitur since complaining about noisiness is pretty rude in the first place so by the time you do, you're already ticked off. But to clarify, ちょっと is not rude at all. In fact, it can be a polite way of getting someone's attention. Certainly better than saying "ほら”, ”あのね” or ”おい!”
I put in 動物のおとは少しうるさいですand was rejected because they wanted 'が’instead of 'は’。In Japanese there is a difference, because the former indicates that it's happening now whereas the latter indicates it's a general statement. However there is no clue in the English original whether it's one or the other. You have to be Obi Wan and use the Force to guess, it seems.
This is the most comprehensive and well-presented explanation of the は and が particles that I've come across so far. I hope it helps! http://nihonshock.com/2010/02/particles-the-difference-between-wa-and-ga/