Apple Says 'Hey Siri' Detection Briefly Becomes Extra Sensitive If Your First Try Doesn't Work

A new entry in Apple's Machine Learning Journal provides a closer look at how hardware, software, and internet services work together to power the hands-free "Hey Siri" feature on the latest iPhone and iPad Pro models.

hey siri
Specifically, a very small speech recognizer built into the embedded motion coprocessor runs all the time and listens for "Hey Siri." When just those two words are detected, Siri parses any subsequent speech as a command or query.

The detector uses a Deep Neural Network to convert the acoustic pattern of a user's voice into a probability distribution. It then uses a temporal integration process to compute a confidence score that the phrase uttered was "Hey Siri."

If the score is high enough, Siri wakes up and proceeds to complete the command or answer the query automatically.

If the score exceeds Apple's lower threshold but not the upper threshold, however, the device enters a more sensitive state for a few seconds, so that Siri is much more likely to be invoked if the user repeats the phrase—even without more effort.

"This second-chance mechanism improves the usability of the system significantly, without increasing the false alarm rate too much because it is only in this extra-sensitive state for a short time," said Apple.

To reduce false triggers from strangers, Apple invites users to complete a short enrollment session in which they say five phrases that each begin with "Hey Siri." The examples are saved on the device.

We compare the distances to the reference patterns created during enrollment with another threshold to decide whether the sound that triggered the detector is likely to be "Hey Siri" spoken by the enrolled user.

This process not only reduces the probability that "Hey Siri" spoken by another person will trigger the iPhone, but also reduces the rate at which other, similar-sounding phrases trigger Siri.

Apple also says it created "Hey Siri" recordings both close and far in various environments, such as in the kitchen, car, bedroom, and restaurant, based on native speakers of many languages around the world.

For many more technical details about how "Hey Siri" works, be sure to read Apple's full article on its Machine Learning Journal.

Popular Stories

iPhone SE 4 Thumb 1

'New' iPhone SE Product Listing Appears on French Website

Wednesday February 12, 2025 6:49 am PST by
As the wait continues for Apple's long-rumored, fourth-generation iPhone SE, French electronics retailer Boulanger has prematurely published a product listing for a "new" model of the iPhone SE. The placeholder page says the device is "coming soon," but it offers no further information, and the price shown is obviously not real. The listing was spotted by a reader of the French technology...
apple launch feb 2025 alt

What to Expect From the 'Apple Launch' Next Week

Thursday February 13, 2025 11:48 am PST by
Apple has yet to announce any new devices this year, but that could change starting next week. Apple CEO Tim Cook today said to "get ready" for a "launch" on Wednesday, February 19. "Get ready to meet the newest member of the family," said Cook, in a social media post. The post includes an #AppleLaunch hashtag, along with a short video featuring an animated Apple logo inside of a circle....
apple launch feb 2025

Tim Cook Teases an 'Apple Launch' Next Wednesday

Thursday February 13, 2025 8:07 am PST by
In a social media post today, Apple CEO Tim Cook teased an upcoming "launch" of some kind scheduled for Wednesday, February 19. "Get ready to meet the newest member of the family," he said, with an #AppleLaunch hashtag. The post includes a short video with an animated Apple logo inside a circle. Cook did not provide an exact time for the launch, or share any other specific details, so...
iOS 18

iOS 18.4 Coming Next Week With These New Features for Your iPhone

Friday February 14, 2025 6:18 am PST by
The first iOS 18.4 beta for iPhones should be just around the corner, and the update is expected to include many new features and changes. Bloomberg's Mark Gurman expects the iOS 18.4 beta to be released by next week. Below, we outline what to expect from iOS 18.4 so far. Apple Intelligence for Siri Siri is expected to get several enhancements powered by Apple Intelligence on iOS...
iPhone 17 Pro Render Front Page Tech

iPhone 17 Pro With All-New Camera Bar Design Allegedly Revealed

Thursday February 13, 2025 5:49 pm PST by
Apple's next-generation iPhone 17 Pro will feature three rear cameras arranged in a familiar triangular layout, but the cameras will be housed in an all-new rectangular camera bar with rounded corners, according to YouTube channel Front Page Tech. iPhone 17 Pro camera design render created by Asher for Front Page Tech In a video uploaded today, Front Page Tech host Jon Prosser said the camera ...
M4 Mac mini Apple Video

Apple's Refurbished Mac Mini Pricing Has a Problem

Thursday February 13, 2025 6:20 am PST by
Apple this week began selling refurbished Mac mini models with the M4 chip for the first time, but this has led to a pricing conundrum. In the United States, Apple is offering a refurbished Mac mini with the base M4 chip, 256GB of storage, 16GB of RAM, and Gigabit Ethernet for $509, down from $599 new. This is the standard 15% discount that Apple offers on refurbished Macs. The issue is...
M4 mini Glowing Blue

Apple Begins Selling Refurbished M4 Macs

Wednesday February 12, 2025 11:35 am PST by
Apple today added MacBook Pro and Mac mini models with M4 series chips to its certified refurbished store in the United States, Canada, the United Kingdom, and Ireland for the first time since the computers were introduced in October 2024. Some refurbished MacBook Pro models with M4 chips are also available in Belgium, Germany, the Netherlands, Spain, and select other European countries. ...
iPhone 16 Apple Store

iPhone 17 in New Sizes This Year: What to Know

Thursday February 13, 2025 2:45 am PST by
Last year, Apple tweaked iPhone 16 Pro screen sizes to make them bigger than 2023's iPhone 15 Pro models, and this year we are also expecting a change in the size of the displays in the iPhone 17 lineup. Here's what we know. Standard iPhone 17 Apple could introduce a new display size for the standard iPhone 17 model in 2025. The iPhone 17 could measure in at 6.3 inches, up from 6.1 inches,...
Apple Ad on X

Apple Resumes Advertising on X

Wednesday February 12, 2025 2:18 pm PST by
Apple this month started advertising on X for the first time in more than a year. The company had stopped advertising on the social media platform in November 2023 following controversial remarks made by its owner Elon Musk. For example, the @Apple account is running an ad promoting Safari's privacy features. The ad was spotted by MacRumors contributor Aaron Perris. The @AppleTV account has a...

Top Rated Comments

TurboPGT! Avatar
96 months ago
There's a lot going on behind the scenes with Siri. I don't think we give her enough credit.
My biggest problem with Siri is not any of the silly one-off bugs that get memed to death on the internet.

My biggest problem was described beautifully in a recent article I read somewhere. About how a voice assistant with 10 possible working commands is great. And one with unlimited working commands is great. But one with hundreds of working commands is terrible, because the user will never know what all those commands are. They will just use the core few that they know. And if they try a command and it isn't one of those hundreds, it causes confusion and doubt.
Score: 23 Votes (Like | Disagree)
seatton Avatar
96 months ago
Soon enough Siri is going to be smarter than Apple executives realizing that the MacMini needs an update ASAP.
Score: 15 Votes (Like | Disagree)
joshwenke Avatar
96 months ago
There's a lot going on behind the scenes with Siri. I don't think we give her enough credit.
Score: 12 Votes (Like | Disagree)
macTW Avatar
96 months ago
Everything about Siri is amazing, and far beyond any competition.

Except her ability to do stuff.
Score: 8 Votes (Like | Disagree)
840quadra Avatar
96 months ago
There has to be something new going on with regards to it’s understanding. After initiating Hey Siri in the car, her comprehension through the Bluetooth system has been notably better for me during the past year. I was wondering if the 7 was doing some machine learning locally, or if the cloud was parsing my questions better with this device. My 5S still struggles with my voice, though it could also be the mics on that device too.

My biggest problem with Siri is not any of the silly one-off bugs that get memed to death on the internet.

My biggest problem was described beautifully in a recent article I read somewhere. About how a voice assistant with 10 possible working commands is great. And one with unlimited working commands is great. But one with hundreds of working commands is terrible, because the user will never know what all those commands are. They will just use the core few that they know. And if they try a command and it isn't one of those hundreds, it causes confusion and doubt.
Apple would help Siri’s reputation a lot, by keeping an active Wiki going for the service, and what commands it will respond to. Because many people have tried to use Siri once for a specific task, found it didn’t work, and since given up. It is really hard for a general user to discover new tricks.

Places like iMore do a decent job of documenting, but, it would be AWESOME if the source had a good manual for it..
Score: 7 Votes (Like | Disagree)
Schizoid Avatar
96 months ago
I just had a quick check on the Mac to see if anything's changed...

Me: "How many files have I opened today?"
Siri: "on the internet I found 'how big is Allah.'"

maybe next year
Score: 7 Votes (Like | Disagree)