Version: 70.0.3538.110
Reproduction Steps: 
1.Turn on Chromevox Control+ALt+Z
2.Find an interesting article. Start reading it Search+r.
3.

Adjust the volume (from hardware buttons, keyboard keys or infernal volume slider on touchscreen. Doesn't matter).
4. Your article will be interrupted by an announcement of the volume's numerical percentage. You will then need to re-issue Search+r to read continously from where you left off.
Changes in volume are inherently evident because the volume of speech ... changes. They should only be announced when Chromevox is not talking nor is media playing. 
Thank you for reading my bug report!
@ChanceyFleet