parrots and t.v.

for those of you with a parrot or two, i ask about my parrot, a dusky conure. I often leave the t.v. on for him as he seems to like the noise and i usually have on P.B.S. and he just chatters away to himself but when certain programs come on he literally has a temper tantrum and when sesame street comes on he goes postal. so what is it? the sound?the voices? i am clueless here.