The short version
Your microphone is analyzed on your device, moment by moment, by a small sound
detector that ships with this page. Audio is never recorded, stored, uploaded, or
sent anywhere: it is measured and immediately discarded. The page's security policy
(connect-src 'self') blocks every network connection except to its own files.
What is stored on your device
sa.settings: your settings (celebrations, vibration).sa.template: your taught doorbell's chime pattern (pitches, lengths, gaps), if you teach one. Not audio, just numbers.sa.history: the recent alerts list (sound name and time).sa.progress: points, badges, streaks, and per-sound counts.sa.welcome: whether you have seen the welcome dialog.
Nothing else. No accounts, no analytics, no cookies. Open the Offline proof button on the home page to see a live log of every network request the page makes, try the app with the network fully simulated off, and delete all of your data with one button.
Microphone
Your browser shows its microphone indicator while the mic runs; a page cannot hide it. The mic turns fully off when you leave the listening screen, when you hide the tab, or when you close the page. Teach-my-doorbell recording runs for exactly 3 seconds and the audio is discarded after the chime pattern is extracted.