How do I enable Silent Mode?

Solution 1:

There's an option in the Settings, although it's a bit hidden:

Go back to the main menu where you can pick your game mode.
Open Adventure (might work in the other modes, too—didn't try).
Pick your Profile (this is profile specific after all).
Press the left action button on your Ring-Con (i.e. B).
Wait for the menu to open.
On the bottom left you'll find a section Settings.
In this sub-menu you can change everything once again, including the run mode, if you move down a bit. (Note that changing the run-mode will force a re-calibration for obvious reasons.)

Here's the whole process in a short clip, note that my system is set to German, but the location of the elements etc. is identical for all languages: