iSpring continues to improve its eLearning development suite of tools. The latest improvement is Text to Speech and it works really well.
To use the Text to Speech feature, first, add the voiceover script to the slide notes. (You'll be able to use this script along with the Text to Speech feature. No retyping, no extra work.)
Select the iSpring Suite 10 tab on the PowerPoint ribbon and click Manage Narration.
Click the Audio drop-down menu and choose Text to Speech.
From the lower left of the dialog box, click the Insert text from notes button.
The script you added to the slide notes earlier appears in the main area of the window.
Select the language and voice from the menus as appropriate. If you'd like, preview the voice by clicking the Preview voice button.