I tried that last hunting season to see if cocking the hammer would spook any game, and it did not. I was standing in the doorway of an old pop-up trailer I use as shelter and had a flock of turkey feeding right in front of me, less than 10-15' away. There were two doe less than 25m away browsing on shrubberies. I repeatedly cocked and uncocked my S&W, not too gently either, and none of the game within hearing range paid the least bit of attention to the sound.
I would suppose that if there is but one animal and it is spooked and the entire world is absolutely silent except for the sound of the hammer being cocked back it may sound like it's at 120 decibels but they rarely take notice if at all.
I have had both Rugers and Smith and Wessons and believe the S&W is the quieter. However, that may be, ummm, 'hear'-say...........................Mikey.