How to Teach Siri to Recognize Only Your Voice
Did you know that the Home Button is not actually needed to invoke Siri? While pressing and holding the button brings her up, you can also configure your iPhone to listen for a verbal cue (“Hey Siri”) when plugged in to a power source.
The new iPhone 6s and iPhone 6s Plus can handle this feature without being plugged into a charger, because their hardware is engineered to do so in an efficient way. Another new thing with iOS 9: You can train Siri to listen to your voice in a more accurate way, possibly blocking other people from triggering the feature with their voice. Here’s a tutorial on how to set up and train Siri.
How to set up SiriSettings > General > Allow “Hey Siri”
Go to your “Settings” app, tap the “General” section and switch on the “Siri” toggle if not already enabled. Then enable the toggle titled Allow “Hey Siri” and your iPhone will launch into the configuration guide below.
How to train Siri
Your iPhone will launch into a configuration procedure when you first enable the “Hey Siri” feature. You can also re-run this assistant by switching off the “Siri” feature entirely, then enabling it again.
The training procedure consists of five units, during which you are asked to say out loud things like “Hey Siri”. Make sure to point your voice in the rough direction of your iPhone and not hold it too close or too far, just as comfortable talking distance.
Apple does not guarantee that Siri will only listen to your voice, but it is rather meant as an enhancement of the detection accuracy, meaning that Siri will react at all, instead of taking your call for help as random noise of some sort.