Since the iPhone 6S, Hey Siri is activated by a dedicated chip in the SoC. This enables low-power real-time detection of trigger words. Before, Hey Siri only worked with phones in the process of charging, because it was done with software, so a lot less efficient.
These voice-activated chips can be trained (as seen in a lot of other phones), but I'm not sure the software-powered Siri can be trained.
Doesn't "trained" in the context of voice recognition mean something more like "better able to understand your voice" and not "able to exclude other voices."
These voice-activated chips can be trained (as seen in a lot of other phones), but I'm not sure the software-powered Siri can be trained.