On iOS, you can activate Siri by saying “Hey Siri.” Vocal activation isn’t available on macOS Sierra through the Siri system preferences, but as Jdcampbell on Reddit points out, it can be done through Sierra’s Accessibility system preference.
Essentially, you use dictation to activate the keyboard shortcut for Siri. The default Siri keyboard command in Sierra is to hold down the Command and Space buttons. You need to change this because the Accessibility feature doesn’t have a way to hold down a keyboard combination.
Change the Siri keyboard shortcut
To change your Siri keyboard command, follow these steps.
Open the Siri system preference (Apple menu > System Preferences).
Look for Keyboard Shortcut in the main window. Click on the pop-up menu. There are two Hold keyboard combinations that you don’t want to use. Apple also offers Press Function Space as an option, but you can’t use it, either. Create a custom shortcut by selecting Customize and then pressing the keys you want to use.
Create a Dictation Command to activate Siri
Now that you have your keyboard shortcut in place, here are the steps to perform to make “Hey Siri” work on your Mac.
In System Preferences (Apple menu > System Preferences), click on the Keyboard icon.
Click on the Dictation tab. If nothing happens, click on another tab, then click Dictation again.
Look for the setting called Dictation. Turn it on. Select Use Enhanced Dictation. You may have to perform a download that allows for offline use.
If you have multiple microphones, you can select the one you want to use by clicking the pop-up menu under the microphone icon. You can also change the language.
Now click the Show All icon at the top of the window (the one with the grid of dots) and then click on the Accessibility icon. (You can also selct View in the menu bar and select Accessibility.)
In the left column of the Accessibility system preference, scroll down until you find Dictation and select it.
Check the box for “Enable the dictation keyword phrase” and you’ll see that the word Computer appears in the long box. Replace it with Hey.
Click the Dictation Commands Button.
An overlay window appears with a Selection list in the left column. Below that is a box for “Enable advanced commands.” Check it.
Click the + button. This will allow you to create a custom command. Enter the following:
When I say: Siri
While using: Any application
Perform: From the pop-up menu, select Press Keyboard Shortcut. The entry box will show “Press keys now” in light gray. Press the keyboard shortcut you use for Siri. In this example, I use Control-Space.
If you press the keyboard shortcut and Siri shows up instead of registering in the entry box, make sure the Accessibility window is active by clicking anywhere on the window.
Customize the vocal command
Now when you say “Hey Siri” to you Mac, a Siri window will open. And if you have your iPhone nearby, Siri will show up on your iPhone, too. You can remedy this by changing the dictation keyword phrase with your own word, like “Hello.”
You can go a step further and change the When I say entry from “Siri” to anything you want in step 10 of the instructions above. For example, I changed the dictation keyword phrase to “Chittychitty” and the When I say entry to “bangbang.” This is what happens:
Remember, this requires dictation to be activated on your Mac. It should activate if you restart your Mac, but if you can’t figure out why Siri isn’t responding, check the Dictation settings in the Keyboard system preference.