I use a laser printer at work. When a print job starts, the printer emits a high pitched whine. It’s obviously a normal sound. What’s making it?
There’s a spinning mirror that scans the laser beam across the page (more accurately, across the drum) This thing spins at a fairly high speed, and is the source of the startup whine. Once it’s spinning at full speed, you don’t notice it all that much as it’s then a steady pitch.
Thanks.
To be a bit more precise, since I have taken many a laser scanner assembly apart, there is a stationary laser that does not move. Then, there is basically a hexagonal mirror attached to the shaft of a small motor. Thing of a normal nut (like you put on a bolt), with a mirror coating on all the sides. The laser is pointed at this rotating mirror, which basically spreads the beam across the width of the developer. Of course there is a bit more involved, but the sound you hear is this high speed motor spinning up.
Beltbuckle (who has one of these mirrors on his keychain)