My own 14 month old is a yeller for fun too. I believe it is a phase that will run its course.
The others often copy him as well at times, and mostly in their highchairs when lunch is over.
I think Judys advice sounds good, I usually just try to ignore the screaming, but I can feel the grey hairs coming in when I do lol
Maybe try singing a very quiet song like abcs. this may make them quiet down to hear what you singing.... temporarly probably lol
