Google introduced for first time voice search on desktop PC for chrome users, You can see a microphone icon in the Google search. Clicking on the microphone icon will enable search through speech recognition, If you vocalized, the search engine gets you the resulting links means users can search the web simply by speaking their requests.
Note:Voice Search is available for US English only, It will take several days for Voice Search to be available to everyone.
But still you can try as an experiment by going to Voice Search Experiment, then click on “Join this experiment” for Voice Search and then go to google.com and voila you can see a microphone icon there. 😎
check out the video below showing a short demonstration on Google Voice Search.