Computer Configuration > Administrative Templates > Google Chrome
Both
HKLM\Software\Policies\Google\Chrome
Setting the policy to Enabled or leaving it unset means that, with the exception of URLs set in the AudioCaptureAllowedUrls list, users get prompted for audio capture access. Setting the policy to Disabled turns off prompts, and audio capture is only available to URLs set in the AudioCaptureAllowedUrls list. Note: The policy affects all audio input (not just the built-in microphone).