If you've used any Android device since Android 4.1 Jelly Bean launched, you'll know just how good Google's Text-to-speech engine is. While some other companies like Samsung have been trying to make their own text-to-speech engines and putting those on their latest devices, they simply don't match up to the quality and clarity that Google's own TTS engine does. Just what is a TTS engine, you ask? Simply put, it's the voice that talks back to you in every part of your phone. When you load up maps and it gives you turn-by-turn directions, that voice is powered by the TTS engine on your phone. When you open Google Now and it talks back to you, that's powered by the TTS engine on your phone. Basically any time the phone has to read any kind of text back to you, the text-to-speech engine is the one doing all the work. Thankfully for phones that didn't receive the Google TTS engine out of the box, Google has officially released it on the Google Play Store, meaning you can clear that horrendous sounding Samsung voice off of your phone.
Head on over to the Play Store link above and get that on your phone ASAP if you're wanting to hear the latest and greatest voice by Google. Once it's downloaded head on over to your system settings by either launching it from the app drawer or from the pull-down notification shade and clicking on the settings button. Depending on the device you have the following instructions might differ a bit.
You'll want to navigate to either "Language and input" or "Accessibility" to find the correct section in your settings menu. From there head to "Text-To-Speech options) and select the Google Text-to-speech Engine. That's it! You can configure a few little settings and even download a few different voices and languages by clicking on the settings cog on the right hand side next to the Google text-to-speech Engine box. Be sure to try it out and enjoy that considerably better voice over the stock Samsung one, or whatever one your manufacturer might have attempted to force on you.