Why does my S8 volume turn down automatically

[AC Question]

Im listening to music or watching a video and the media plays normal for the fort coyple seconds and then turns down on its own right after? Does not happen if i plug in headphones.

 

[Fingerblaster]

I also get this... No resolution yet except killing the browser and replaying.

Massively clutching at straws but seems to be related to when I'm in a noisy environment. Not sure if it's some clever setting that stops video noise playing when in a loud environment to save embarrassment, but couldn't find a setting to change this....