Starting with iOS 8, Siri can be made to work more like Google Now in the sense that you can invoke Siri just by saying “Hey, Siri” or something close. That is, you don’t have to tap and hold the home button to open Siri. It’s called Voice Activation.
In the current implementation, this works only when you have your iPhone/iPad plugged into a power source (or your computer). Obviously, this is to preserve battery drain issues.
We’re hoping this feature would spill over so that you can have “always on” Siri even when your device isn’t plugged in (at the cost of the battery of course, but still a good feature to have.)
How to Disable Siri on iPhone or iPad
Requirements: iOS 8 running on iPhone 4s, 5, 5c/5s, iPad Air/4th/3rd or iPad mini 1st/2nd.
Step #1. Open the Settings app on your iPhone/iPad.
Step #2. Tap on General.
Step #3. Now, tap on Siri to open Siri settings.
Step #4. Make sure Siri is enabled (Switch on.)
Step #5. To turn on voice-activated Siri, switch on Voice Activation.
Note that Voice Activation only works when your iDevice is connected to a power source.
And to turn it off, switch off voice activation.
Watch out how to enable ‘Hey Siri’ handsfree mode in iOS 8.x:
The way Voice Activation is designed right now looks like it’s focused on in-car Siri accessibility. You can’t be tapping on the phone to access Siri when you’re driving.
So, with Voice Activation and your iPhone connected to a car charger port, you can just call up Siri and start accessing your phone through it, hands-free. Of course, this is for those cars that don’t support CarPlay, iOS’s latest high-level integration with in-car systems.
That’s all there is to it!