When you refer to a sound as being “raucous” what you mean is that it is loud and harsh. It is very unpleasant to listen to.
The first syllable is pronounced like the word “raw”. The “c” is like the “k” in “king” and the following “ou” is like the “a” in “china”. The main stress is on the first syllable.
*The raucous cry of the birds woke him up early in the morning.