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
Obtain A Mac On Speaking Terms
Among various incredible features of the Mac OS X, the inclusion of various types of human-like voices coupled with text-to-speech (TTS) plus the speech recognition applications which has the ability to covert the Mac OS X into a machine participant which has vocal effects in it as a part of the everyday computing requirements of a user. The setting of the TTS software can be accessed via the System preference menu and then selecting the Speech option. Choose the Text to Speech page and a voice from a range of six voice presentations. There are various other options in the Snow Leopard if the user selects the Show More Voices options, whereas, in the Mac Lion 10.7 OS X model, the feature of customizing a voice presentation is also added up.
Another feature is that the user can easily select the option as to whether he/she wants the system to pipe up or not. Moreover, select various other options such as announcing of important applications which requires the attention of the user, announcing of alerts on the Mac system, or simply speaking out whatever text has been selected after the user has pressed the configurable hotkey that is pre-defined by the user.
Vocationally, turn the VoiceOver on and off by the help of Command-Fn-F5 keys and by configuring it by the use of the program VoiceOver Utility. The VoiceOver has the ability to wear out its welcome without any sort of tweaking in it, but, all those who have to struggle quite a lot in order to read the contents on the screen; it can turn out to be of great help.
The feature of Automator is inclusive of a Speak Text action where the talking of third-party apps is also enabled. The notification engine of Growl has the feature to speak out alerts if the notification type is set to “Speech”.
There are settings in the Mac OS X where the user can even set the time when he/she wants the announcement to be made. Switch to the Date and Time options and select Clock preferences panel in order to set the Mac settings to announce the time at given intervals. Another option can be the option of Universal Access > Seeing preferences panel in order to control the features of VoiceOver which speaks out whatever content has been selected on the screen.
Although, the application is incapable to provide features that are extensive as compared to the third-party applications such as the Dragon Dictate software, still, the voice control features of the Mac OS X can be considered as a quite useful alternate for the keyboard and mouse system controls.
The next step is to launch the Speech Recognition panel and turn-on the “Speakable Items”. Select the settings option and select a microphone. A tip here is that the option of headset – and – microphone has the ability to offer clearer voice recognition.
Furthermore, a Listening Key is also required which should compulsorily be pressed when the user is about to speak a command. This listening key is by default set at the ESC key, but, can be changed quite easily according to the users’ requirement. You can also click “Listen continuously with keyword” if the user preference lies in the spoken command in order to inform the Mac OS X that a command has been lined up for it.
Whenever, the voice recognition option is enabled, a round shaped microphone type icon appears on the screen plus a recognized command will be clearly displayed on the top of the icon. The commands considered basic by the system such as ”Switch to Mail” or Open iTunes” result will turn out to be exactly as expected as it will allow the user to customizes those commands that are recognized by the system by simply clicking on the Commands page and then selecting or deselecting the particular forms of contents the Mac OS X must be listening.
For example, if you require inserting a page break in a Word document, the TTS application will work as follows. Firstly speak out the terms “Open Microsoft Word” and after the insert menu, then “break: and then “Page Break”. Moreover, if the user requirement is to see as to which commands are present in a given application, click open the Speakable Items folder tab.