Why do flies buzz when they fly?

Question

Why do flies buzz when they fly?

Answer 1

Because they move their wings in air.

Answer 2

it is the sound from their wings beating so fast, that it makes a buzzing noise

Answer 3

its the sound of their wings flapping so fast it makes that buzz sound you hear.

Answer 4

It's because their wings beat so quickly. You can hear hummingbirds, too, if you're close enough.  

Answer 5

Fly used to refer to any insect that could in fact fly and still refers to house fly, horse fly, fruit fly, deer fly, dragon fly and tsetse fly etc.  Certain insects (flies) beat their wings and disturb the surrounding air with a frequency within the range of human hearing (if close enough).  Luckily we can often hear mosquitoes (Slap!).  

Answer 6

flies doesn't have joints as birds... so their wings are straight and erect... so while flying they flap or shake their wings very fast to go higher and higher which makes a buzzing sound...