Emanuele Bartolomucci noticed an interesting feature in Google Translate. If you click the "listen" button next to the text you want to translate or the translation, Google converts the text into speech. Click "listen" again and the speed decreases, probably because Google assumes that you are listening again to better get the correct pronunciation. It's like asking Google: "Could you speak more slowly, please?"
If you click "listen" the third time, Google goes back to the normal speed. Click again and the speed decreases. The two text-to-speech versions alternate.
If you will check Google Translate's URLs and the second version has the following parameter: "ttsspeed=0.24", which changes the text-to-speech speed.