Here is how you can cast @Voice reading aloud (or any other sound playing app) to your Google Home speakers:
 
-  Open Google Home  app on Android device
-  Press the “Account” button at bottom-right (person in a circle icon)
-  Scroll down if necessary, press “Mirror device”
-  Select the speaker you want to cast to on the next screen
-  Now switch to @Voice app and start reading aloud, the voice goes to your speaker
-  You may stop casting at anytime from the Google Home notification on your phone/tablet.