This problem occurred to me when I flashed my Galaxy S II with Pure ICS Custom Rom and it uses Android AOKP keyboard. Everything works perfectly except for the keyboard, it has no sound. After hours of searching and tinkering I found out that by default Android stock keyboard sound setting is unchecked. So how to enable keyboard sound on Android keyboard? it’s simple follow this instruction.
How to fix Android AOKP keyboard has no sound
Settings > Language and Keyboard > Android Keyboard > tack the option in the right most part (see image below for clearer view) > Sound on Keypress