I just installed the Roku Express, and it generally works well, but when I try to watch the news through the "NewsOn" app, the audio will suddenly become rapid, sounding like a high pitched "chipmunk" voice. I back out of the app and relaunch the news, but it happens again and again. I have never had this problem with "NewsOn" through Amazon Fire TV, nor with my older Roku devices.
I had the same problem. I was using the Screen Reader in Accessibility to make the sound correct itself. That is not a true fix.
To fix the chipmunk sound, go to Roku Home, Settings, Audio, Digital Output Format. Change the setting to Audio. This should resolve the problem.