Voice Feedback
WARNING: This page is about a different car, the 2005 Buick LaCrosse and 2005 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The OnStar® Personal Calling (OPC) system has the capability of responding to the user with either an automated voice response or with a tone or beep. These 2 types of responses can be switched back and forth by pressing the Answer/End Call button, waiting for the system to respond "OnStar Ready" and speaking the phrase "voice feedback". The system will then respond, "voice feedback is now ON/OFF".