The short, simple answer is that your automatic watch, even when brand new, makes noise. Have you seen a picture of the inside of an automatic watch? Check this out:
Automatic Watches are Complex Machines
As you can see, automatic watches are a complex arrangement of gears, levers, and bearings. Just like any other piece of equipment you can think of with gears, levers, and bearings, your watch will make some noise just from normal operation. From the friction of the gears to the swooshing of ball bearings in their races, some level of noise is completely normal. Luxury watches, expensive watches, and watches with thicker cases in general will keep more of the noise inside of the watch and it will be less noticeable to the wearer.
Also, even if it appears as if your watch hands sweep, unless you have a very special Grand Seiko watch, the hands in your watch actually tick. Even if this ticking is not noticeable visibly, it is not silent, and it can contribute to any sound you hear.
Automatic Watch Rattle
Also, as you move your arm or the watch, or if you shake your automatic watch, you may notice that the sound changes a little bit. This is sometimes referred to as an automatic watch rattle. Again, this is perfectly normal. Not only may the orientation of the watch relative to the ground change the way various parts in the watch interact due to gravity, but as your watch ages some parts may become just a little bit more loose than when new. In fact, some of the rattle that you hear may be from the wrist band or where the watch band interacts with the watch case.
Could The Noise Indicate Damage Inside The Watch?
Indeed, you may have a damaged watch. However, this is far from certain just because your automatic watch makes noise or rattles when shaken. If your watch was recently struck, or if you are having other problems such as time or date accuracy, you should certainly get your watch inspected by the manufacturer, retailer, or watchmaker.
You may have read other places online about a rotor axle rubbing inside the watch, and/or about small bits of metal debris interfering with the gears or bearings. From our point of view, trying to figure out exactly what the problem is with your watch is a bad idea. Unless you are a watchmaker or skilled watch repair person, you do not want to be opening up your automatic watch. There is almost zero chance that any problem can be fixed by you! If your watch isn’t performing well, if the noise has changed or worsened, or if you know your watch endured a rough shock, your best bet is to get the watch to a watch professional for diagnosis and repair.
Automatic watches are complex machines. Complex machines tend to make noise! The more expensive the watch, the less of that noise will make it to your ears. From the ticking of the mechanism, to the bearings zooming around their races to the gears engaging each other, your watch makes noise the entire time it runs. And that is perfectly okay.
Grand Seiko Watches with Their Unique Spring Drive Movement