Google is updating the voice behind the Search for US English. The new voice is noticeably better, as it is smoother and there is less gaps between words. The change appears to be in the server-side part of the Google Text-to-Speech engine, since there aren't any updates for the Google TTS and Google app in the Play Store. Check out the video below to hear the difference in the new voice versus the old one. Source | Via
Source: http://www.gsmarena.com/new_voice_update_hits_google_search_for_us_english-news-17398.php