I have this same issue, there is much disparity in the volume of some channels vs others
What's most frustrating is when the volume is low, especially when trying to listen to music performances, and no matter how high I kick it up, it only barely increases. So while 35 may be very loud on some stations, as high as 75 on another is barely audible! Why is there so much disparity, and why can't there be a simple sound normalization feature that would take care of it?
I have the issue with my hisense roku tv, where the volume must be turned all the way up to 80 in order to hear what is being said. I see a whole lot of people with the same issue, but have seen ZERO solutions or even replies from Hisense or Roku.
Have you tried contacting Hisense support yet to inquire further? I'd suggest starting there to see what options or suggestions they can provide. Each Roku TV manufacturer provides direct support and warranty services for their products running the Roku OS.