Handwashing on Apple Watch Is Useless
By far, the most disappointing and useless feature on the Apple Watch is the Handwashing Timer. Which is ironic, because when it was announced back in 2020 I thought it was a really neat idea.
The problem: the trigger… doesn’t trigger.
Apple says the trigger is audio and motion, so it probably detects the sound of running water, then checks if the user is rubbing their hands together.
But this never works reliably. When it does work it is magical. But more often then not it thinks I’ve only washed for five seconds when I’ve already scrubbed for forty seconds trying to get it to trigger, or won’t trigger at all.
And there are false positives: any rubbing motion while water is running sets it off. So it activates when you’re washing dishes, for example.
My naive solution: when the Apple Watch hears the sound of running water, prompt the user if they’re washing their hands. But since we obviously can’t touch the watch with dirty hands, have the user do some sort of gesture to start the timer. Maybe like a double-chop in mid-air, just like the Motorola phones that wait for the gesture to turn on the flashlight?
This solves the issue of false positives, since users can just not do the gesture to not start the timer if they’re not washing their hands, and it also means it’s easier to trigger, since the only condition to fulfill is to get the Apple Watch to hear the sound of running water.
So after a ton of trial and error, I got frustrated enough to research exactly what the trigger for handwashing on the Apple Watch is. And it seems like it isn’t water.
The system uses machine learning models to tackle different methods, but the system gets an additional nudge from the Watch’s microphone. Along with motion, the app listens for the sound of running water. Even that’s not enough, though — after all, eco sinks have become increasingly popular, meaning that there’s often less water sound to be listening for. The sound of squishing soap takes care of that last bit. It’s got a unique enough audio signature so as to confirm that handwashing is taking place.
Handwashing detection uses a combination of wrist movement and ambient sound tracking to make its determinations. Apple says that the unique squelching sound of soap is one of the main indicators. (…)
(…) And the Apple Watch will now track your hand-washing in two core ways: It will monitor and listen for the soap pump, as well as water and wrist movement, to ensure you’re washing your hands for 20 seconds, and will remind you to wash your hands when you return home. (…)
Which makes a ton of sense, because then the Apple Watch wouldn’t detect any handwashing sessions where the water has been switched off, so as to not waste any. So I tried making the squelching sounds obvious as much as possible during handwashing, and it seems to have improved the detection rate by quite a bit. I haven’t been nerdsniped to such a degree as to actually track the detection rate, but in my subjective thoughts I think the rate has gone from 10% to around 70 or 80%.