Just recently (maybe the last couple of weeks) I have noticed a very odd audio glitch sometimes when I stop watching either live or recorded tv in channels. It’s repeatable. Just set a video stream going then on iOS press be home button on the device or on tvOS press the home button to exit. Where the audio used to fade gracefully it now does a weird echo chamber style thing. Works the same across iPad, iPhone and Apple TV 4K.
This is on iOS 11 and tvOS 11 latest public releases and latest public build of channels.