I have a Nikon D5500 and I have been using it for about 3 months. Every normal shot should have a beeping sound when pressing the shutter release button half (which is to let the camera focus if auto focus is on) right? But mine doesn't, it acts like the quiet shutter release option on the single frame option (or Continuous). This acts like the quiet shutter release option, but why?? Please help. Thank you.
There is a beep with auto focus, which can be turned off at Setup menu Beep Options.
This is described on page 276 of the D5500 Reference Manual (much larger than the User Manual), which is free from Nikon at http://downloadcenter.nikonimglib.com/en/products/196/D5500.html
The beep is actually a focus confirmation indicator, not a focus activation indicator. If you are in AF-C mode (which does not confirm AF as it continuously updates focus until the shot is taken) or have AF turned off on manual focus mode the beep, even if enabled in the menu, will not sound.