There are three built-in ways to activate Siri on a Mac, but all require you to click your mouse or the keyboard. If you'd rather say, "Hey, Siri," the way you can with the iPhone, there's a workaround.
Before we go through your options for calling up Siri, let's first make sure you have Siri enabled. When you installed MacOS Sierra, one of the setup screens asked if you wanted to enable Siri, so it's likely Siri is ready to go on your Mac. If you declined Sierra's initial Siri offer, go to System Preferences > Siri and make sure the box is checked for Enable Siri.
With Siri enabled, here are the four ways to activate Apple's voice assistant:
Option 1: The Siri icon in the Dock
Easy-speasy. Click the Siri icon in the Dock and the Siri window will spring forth.
Option 2: The Siri icon in the menu bar
If you don't see a Siri icon in the menu bar in the upper-right corner of your screen, then go to System Preferences > Siri and check the box for Show Siri in menu bar.
Option 3: Use a keyboard shortcut
The default keyboard shortcut for activating Siri is pressing and holding Command-spacebar. You can set your own keyboard shortcut, however, in System Preferences > Siri.
Option 4: Enable 'Hey, Siri'
Apple doesn't offer a switch to enable the "Hey, Siri" command with MacOS Sierra as it does with iOS 10, but there is a workaround that Reddit user jdcampbell found. In a nutshell, you need to create a custom keyboard shortcut for Siri and then set up a dictation command to activate that shortcut.
In detail, here are the steps to create the "Hey, Siri" command:
Step 1: Go to System Preferences > Siri and choose a custom keyboard shortcut. (Dictation doesn't understand pressing and holding a key, so you need to choose a keyboard shortcut other than Apple's default shortcut for Siri. And for reasons that escape me, dictation didn't recognize Apple's suggested keyboard shortcut of Function-Spacebar.) For my custom Siri shortcut, I chose Command-S.
Step 2: Go to System Preferences > Keyboard and click the Dictation tab. Turn on Dictation and also check the box for Use Enhanced Dictation. (You may need to download and install a file for Enhanced Dictation if you haven't used it before.)
Step 3: Go to System Preferences > Accessibility. Scroll down in the left panel and click Dictation. On the right panel, check the box for Enable the dictation keyword phrase and then change the phrase from Computer to Hey.
Step 4: Staying on the Accessibility page, click the Dictation Commands button. Check the box for Enable advanced commands and then click the "+" button to add a new command.
For your new command, use these settings:
- When I say: Siri
- While using: Any Application
- Perform: select Press Keyboard Shortcut from the menu and then enter your custom Siri keyboard shortcut (mine is Command-S).
When you are finished, click Done to save your changes.
This workaround didn't work for me at first, but after I went to System Preferences > Siri and unchecked and then rechecked the box to Enable Siri, I was all set.
One last note: If you are using the "Hey, Siri" command with your Mac, your iPhone may activate Siri if it's within earshot. You aren't stuck with the "Hey, Siri" command, however, and can set up a different command to keep your iPhone and Mac from both springing to action on the same command. May I suggest "Yo, Mac" or "Hello, HAL" perhaps?