how do i turn the volumn up for certain apps like maps on the left side of phone to hear waze speaking

No, when using maps, waze etc, the voice comes on. I can use my volume down or up to turn the voice up etc. it shows on the left side of the phone. Little white line. But if the volume is down you have to guess when they start telling directions etc to turn it up. If you put waze on and press the up volume button, it only shows the ringer (top of screen) volume. Hope I explained it enough I always have end and restart the app and catch it right away to get them to talk so I can raise the volume. TY