I think that it largely depends on the type of buttons the printer is operated with. One way or another, it is better for each of the buttons, or group of similar buttons, to have as different a response (look, feel and sound) as possible.
On a printer, for example, it is advisable for the "print" button to have a distinct colour, shape, size and ideally also sound and texture from the other buttons. Arrows could then have their own set of characteristics and so on for each group of buttons.
That way one can operate the device purely by touch, as well as for example to describe someone easily what they should do ("Press the big green circle to print.") The sound of the button then reassures us that we did the right action.
That sound may come from the physical button itself, but if all buttons are identical, or product a similar enough sound (e.g. like buttons on the computer keyboard), an additional sound generated by the device may be a good idea, both to reassure yourself every time you use the button (I heard a beep = the text will be printed.) and to reassure those you explain it to ("You'll hear a beep if you did everything all right.")