I'm not hearing impaired but that doesn't prevent me from taking advantage of certain VoiceOver features on my iPhone. For instance, I sometimes use Speak Selection to get iOS to read a book to me as I'm surfing the web, or doing something else.
Being a non-native English speaker, I also rely on that feature to have my iPhone read aloud words and phrases whenever I'm unsure about their correct pronunciation, which is a lot of help—especially with the adjustable pitch and speaking rate.
Starting with iOS 8, a number of options for the Siri voices you can use for the VoiceOver, Speak Screen and Speak Selection features became available. This tutorial explains how to choose a voice for Speak Screen and Speak Selection and adjust voices for VoiceOver.