hi anandisrocking007 ,
The voice recognition process happens in the extention's tab. As you mentioned, if you close the tab the voice recognition stops. This is expected. It works in that way to simplify the microphone's permission request. You only allow to the extension tab to listen to you, otherwise, this same permission would be required per each website you open.
Thanks for playing with the extension. I hope this limitation doesn't bother you too much, it's a Google Chrome restriction we can't overcome.