The app can be used to read content on your screen and read aloud books purchased from the Google Play Store. When used with Google Translate, you can hear the correct way to pronounce a word spoken in a foreign language.
To change the voice on Google Text-to-speech, go to Settings > Language & input > Text-to-speech output. Next to "Google Text-to-speech Engine" you will see the Settings icon (a gear). Click on that, and tap on "Install voice data." From there, select the language that you want to use, and you will see what choices you have for the vocals.
It is possible that the update hasn't reached you yet, and if you're the impatient type, you can click on the sourcelink to install the APK. Click on the slideshow if you want to see what the updated version of Text-to-speech looks like.
source: GoogleText-to-speech (APK) via AndroidPolice