Loading... Please wait...Most of the silent kinds of alarm clocks are digital, they do not have moving clock mechanism’s and so do not make any noise, the reason for this is because they are all run from accurate electronics which displays the time digitally on either an LCD screen or LED screen. The other type of popular silent alarm clocks are specially designed analogue clocks with silent sweep dials, this means that the clock hands, even the seconds hand make no or very little noise when they show the time.