I stumbled across this reddit post (
https://www.reddit.com/r/unitedairli...ght_bluetooth/) yesterday - one of the comments is from a flight attendant, who said they have the ability on some aircraft to adjust the baseline volume for your particular seat if it's too low:
Flight attendant here - Depending on the aircraft, we have the ability to adjust the volume level of each specific seat. Like it’s at a default level that lets you adjust your volume, but we can increase that level that changes your range, if that makes sense. I’ve had to turn seats up for people before. (Some crew may not know how to do this, but it’s on our touch screen where we can reset the monitors and parental controls.) So, you can ask for that to be done.