When I put my camera (d610) in Quiet mode my ears play a trick on me I think. The shutter sounds so much slower when in Q than in regular Single or Continuous. Everything is still the same correct? Or does anything change besides the sound?
Are you sure that it's your shutter you're hearing and not your mirror? Because typically the mirror would make more noise than the shutter (assuming you're shooting through the viewfinder)
The shutter will operate at whatever shutter speed you or the camera selects to take the photo. But the mirror that moves out of the way immediately before the shutter opens will move out of the way more slowly. Depending on how quite mode is set up in your camera after the shutter closes the shutter reset may be delayed until you pull your finger up off the shutter button to release the full press.