Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
How to Use Dictation in OS X Mountain Lion
If you have difficulties typing or are simply too lazy and want someone else to do it for you, dictation tools provide an alternative method, relying on vocal recognition to automatically type as you speak. One of the great things about Apple’s OS X Mountain Lion update was the fact that it came with its own dictation software. Dictation is very easy to set up and use and will work literally anywhere where typing is required. Here is how to use it:
First of all you need to set it up so start by opening up your System Preferences and then select Dictation & Speech.
This will open up the Dictation & Speech menu, which features options for both Dictation and Text to Speech.
Under Dictation set it to On.
Here you will also be able to designate a shortcut to switch Dictation on, but by default it can be accessed by pressing the Fn key twice. You can also select the language you will be speaking in. Choosing the wrong language will result in highly inaccurate interpretations when you speak.
When it comes to putting Dictation into action, open the application that requires you to type text and activate it using your chosen shortcut. Make sure the cursor is in the right place before you start.
A microphone icon will pop up under the cursor, indicating that Dictation is ready to use. Now you can start speaking. You will not see any text appear at this point.
When you are finished and wish to transcribe it to the screen, either use your shortcut to stop or click on the Done button below the icon. Within seconds everything you said will appear in the designated area. It may not be perfect but you will be able to edit it manually.
When it comes to punctuation there are various vocal commands you can use that will allow you to format as you speak. For example, saying “new line” or “new paragraph” will include the desired effect in your document when it is transcribed. There are many other self-explanatory commands, such as “caps on/off”, “question mark” and so on. If you speak it, it will appear.
Before you can use Dictation however you will need to make sure you are connected to the internet as this function is not performed entirely on your computer. Everything you say is sent to an external server before the transcription comes back to you.
It is also a good idea to get a higher quality external microphone. While the microphone integrated into your Mac is more than adequate, you will find an external microphone does a much better job of recording your voice clearly, which in turn will provide a more accurate transcription.
To determine which microphone you will be using when you have more than one at your disposal, go to the Dictation & Speech menu. There is an icon with a drop down menu under it, which will allow you to choose one when clicked.