Mac OS X comes with time announcement utility tucks inside System Preferences > Date & Time. To enable this feature, access the preference page and click to check the box “Announce the time” as shown above. You can choose to have time announcement on the hour, on the half hour or on the quarter hour.
Click the “Customize Voice…” button to customize the voice if you do not like the default system voice. You can customize the volume, speed of speak or select different male/female voice.