You can use the Voice  setting (under Avaz Settings > Voice settings) to moderate the selected voice, to make it sound more masculine or feminine to make it nmore appropriate to the user's voice and age. 

  1. Tap the Menu button (screenshot 1)
  2. Tap the Settings button (screenshot 2)
  3. Select the Voice from Audio settings
  4. Note that Avaz Android offers Readspeaker voices while Avaz iOS offers Ivona voices

Screenshots from Avaz ver 6.6

Screenshot 1: Menu button

Screenshot 2 - Settings button

Screenshot 3 - From Audio Settings, tap the Voice option

Screenshot : Default voices

Screenshot: Select the voice from Default voices > English > Voice 

For versions less than 6.6 you can use  Avaz Settings > Voice settings to change the voices. 

Related articles:

Avaz FAQ: How to change to Indian language voices?

Avaz FAQ: How to change the voice or accent to suit the user?