[robterrell]

Siri is definitely not trained to a single voice. And yes, the car radio can turn it on. I've had a podcast discussion of Siri trigger it. It became such a joke that some podcasters have another phrase they say when they mean "hey Siri".

[Artemis2]

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.

[XorNot]

"Trained" is a bit of a joke with voice-activation. I've never seen it matter in practice.

[gherkin0]

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."

[dorfsmay]

I think Google does for android. I often ask "wake me up in 15 minutes". I've seen the phone write 50 and immediately switch to 15.

[knn]

trained to a particular voice ~= trained to a user's preferences!

[fencepost]

As a sample of the alternate term, Merlin Mann's assorted podcasts generally use "Ahoy Telephone."

[legulere]

It has only been a feature since iOS 9: http://9to5mac.com/2015/09/11/os-9-siri-voice-recognition-tr...