My dell latitude C840 is not bringing out voice again

I figure there are two possibilities here. First, there is an Fn function on the keyboard that will enable/disable the speakers on command. This function is shared with the "End" key at the upper right of the keyboard, and is used in conjunction with the "Fn" key, found next to the left "Ctrl"key. Holding down the "Fn" key while pressing the "End" key will toggle the speakers on or off. Second, there is the possibility that the headphone jack has been physically damaged while the headphones were plugged into it. That jack has internal switches that disconnect the speakers while headphones are in use. If the jack is damaged, the speakers will not operate. Unfortunately, most repair shops are not equipped to replace this jack, and the jack itself is nearly impossible to buy for replacement anyway. Hopefully your problem is just the "Fn" key.