The iPhone has dedicated low-power on-device hardware that is trained to pick up "Hey Siri" exclusively. It only wakes up the rest of the device and captures additional audio after that wake word has been triggered.

https://machinelearning.apple.com/research/voice-trigger

https://machinelearning.apple.com/research/hey-siri

>pick up "Hey Siri" exclusively

until it isn't. anything apple is proprietary and any feature could silently change at any time even for only specific devices/user.

https://web.archive.org/web/20250415140321/https://www.thegu...