From Verizon forums:
https://community.verizonwireless.com/message/945051
JerseyK Mar 14, 2013 7:50 PM (in response to Artoro)
I had the same problem when I got the update, but with haptic feedback rather than sound. I followed 21stNow's advice (thank you!) and was able to control it as follows:
Settings -> Language and Input (under the "Personal" heading) -> ["settings" icon next to "Samsung Keyboard" ] -> Advanced -> Key-tap vibration (checkbox)
That turned off haptic feedback for me, and there's a checkbox for "Key-tap sound" right below it that will hopefully turn off sound for you.