See this Amazon post for more details and some examples
"Amazon already gave Alexa the ability to whisper, and now it’s rolling out another way to change the assistant’s speaking style — it’s giving Alexa a “newscaster” voice. Starting today, when U.S. customers ask Alexa “what’s the latest?” to hear the day’s news, Alexa will respond using a voice that’s similar to how a professional newscaster delivers news.Alexa gets a professional 'newscaster' voice for reading the day's news | TechCrunch
The voice knows which words should be emphasized for a more realistic delivery of the news, explains Amazon.
To achieve this new voice, Amazon took advantage of recent developments it made with Neural TTS technology, or NTTS. This technology delivers a more natural-sounding voice, and allows Alexa to adapt her speaking style based on the context of your request. For the newscaster voice, NTTS produced speech with better intonation that emphasizes the right words in a sentence, Amazon says."