that didn't work, and the issue appears to be site-wide so i suppose there's two possibilities:

a) youtube has made some internal change to reduce the volume.

b) i'm being targeted.

i guess we'll have to see if other people have the same problem or not.

i could plug this chromebook into the amplifier in the other room, but that would be annoying. so, i'm going to wait a few days and see if i can get a headphone amp, instead, if i have to.

if you've also noticed that the volume on youtube has decreased substantively site-wide, please post somewhere so i can see it.