This is what I found with a quick Google Search. Note what it says about the screen as well.
iPhone 6s stops listening for 'Hey Siri' when it's in your pocket or face down on a table By Neil Hughes Thursday, October 22, 2015, 11:21 am PT (02:21 pm ET) Apple's new iPhone 6s utilizes its M9 coprocessor for "Hey Siri" input, allowing it to always listen for voice commands. Well, almost always. In years past, Apple's motion coprocessor has been used to silently and constantly track steps and activity. But starting with this year's A9 CPU in the iPhone 6s and iPhone 6s Plus, the M9 component also listens for voice. With earlier iOS devices, "Hey Siri" requires an iPhone or an iPad connected to external power to prevent draining battery life. But the M9 enables the iPhone 6s to always listen for "Hey Siri" commands — except when it doesn't. Though it's not noted in any of Apple's promotional materials, "Hey Siri" does not work on the iPhone 6s when it's laying face down, or is inside a user's pocket. Presumably, the iPhone 6s proximity sensor, located near the earpiece above the Retina display, is also constantly utilized to change when the device is available for "Hey Siri." Starting with iOS 9, Apple also utilizes the proximity sensor on all iPhone models to prevent the display from turning on when the handset is lying face-down or within a pocket. Displays are typically the most power-hungry component on an iPhone, and keeping the screen dark when a user cannot see it is a practical way to extend battery life. Similarly, it's unlikely that a user will want to invoke "Hey Siri" when their iPhone is in their pocket, where the device's microphone and speaker could be obstructed. Users who want constant access to "Hey Siri" with their iPhone 6s or iPhone 6s Plus should perhaps get into the habit of laying their handset on a table face-up. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jeremy Sent: Monday, July 4, 2016 4:34 PM To: [email protected] Subject: RE: HI Siri - Does it drain battery No, my phone is not plugged into anything, and all I have to do is say "hi Siri." JR -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Billy Maynard Sent: Monday, July 04, 2016 4:27 PM To: [email protected] Subject: Re: HI Siri - Does it drain battery hi, This feature I beleave can only be activated when plugged into power. so, it really won't drain battery. ----- Original Message ----- From: "Jeremy" <[email protected]> To: <[email protected]> Sent: Monday, July 04, 2016 6:13 PM Subject: HI Siri - Does it drain battery > HI all, > > Does the "Hi Siri" feature on newer iPhones drain the battery? I'm > assuming the microphone is always on or listening and this uses > battery power, is this true? > > JR > > > -- > The following information is important for all members of the V iPhone > list. > > If you have any questions or concerns about the running of this list, > or if you feel that a member's post is inappropriate, please contact > the owners or moderators directly rather than posting on the list itself. > > Your V iPhone list moderator is Mark Taylor and your owner is Cara > Quinn - you can reach Cara at [email protected] > > The archives for this list can be searched at: > http://www.mail-archive.com/[email protected]/ > --- > You received this message because you are subscribed to the Google > Groups "VIPhone" group. > To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/viphone. > For more options, visit https://groups.google.com/d/optout. -- The following information is important for all members of the V iPhone list. If you have any questions or concerns about the running of this list, or if you feel that a member's post is inappropriate, please contact the owners or moderators directly rather than posting on the list itself. Your V iPhone list moderator is Mark Taylor and your owner is Cara Quinn - you can reach Cara at [email protected] The archives for this list can be searched at: http://www.mail-archive.com/[email protected]/ --- You received this message because you are subscribed to the Google Groups "VIPhone" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/viphone. For more options, visit https://groups.google.com/d/optout. -- The following information is important for all members of the V iPhone list. If you have any questions or concerns about the running of this list, or if you feel that a member's post is inappropriate, please contact the owners or moderators directly rather than posting on the list itself. Your V iPhone list moderator is Mark Taylor and your owner is Cara Quinn - you can reach Cara at [email protected] The archives for this list can be searched at: http://www.mail-archive.com/[email protected]/ --- You received this message because you are subscribed to the Google Groups "VIPhone" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/viphone. For more options, visit https://groups.google.com/d/optout. -- The following information is important for all members of the V iPhone list. If you have any questions or concerns about the running of this list, or if you feel that a member's post is inappropriate, please contact the owners or moderators directly rather than posting on the list itself. Your V iPhone list moderator is Mark Taylor and your owner is Cara Quinn - you can reach Cara at [email protected] The archives for this list can be searched at: http://www.mail-archive.com/[email protected]/ --- You received this message because you are subscribed to the Google Groups "VIPhone" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/viphone. For more options, visit https://groups.google.com/d/optout.
