What are those insects that are noisy every summer? they usually fly from tree to tree?

Question

they look similar to cicadas,

Answer 1

i think your talking abbout locust or circadia not katydids

Answer 2

It is likely a cicada, if they are that noisy. They do have a periodic life cycle of 13-17 years. it appears to be 7 not every last cicada comes out at once, they are staggered in birth years. Locusts don't have this periodic life cycle.  

Answer 3

Katydids.

Answer 4

Cicada's, I think, and yes, they are very noisy. Locusts are the one that come every seven years.  

Answer 5

Cicadas

some species come every year, others come out every so often.

In fact where I live, the most common species (dogday harvestfly) comes out every year