Why do some flies make noise when they fly, and sometimes they make no noise?
101572
They are not making sound with their mouth but it is the sound produced by the fast movement of their wings.
818797
Most bats (or at least many, many bats) generate a very high pitched sound called an 'ultra-high frequency sound'. Say that someone sings a note. Then the note keeps getting higher and higher and higher. After a time, the note would be so high that people couldn't hear it, BUT IT WOULD STILL BE A SOUND. It is just a high sound that you can't hear. \n\nOk, so bats have this little thing in their heads, usually behind their noses, that makes these sounds. Most of the time, the bat's noses are shaped like little speakers, or little trumpets, so that they can send this sound out better. Then, in order to hear the sound that comes back, or echos back, they have big ears. If you'll notice, the little yellow baby bats here have really big noses, and really big ears. This echo that they hear when the sound comes back gives their technique it's name of 'echo-location'. When the sound that they send out hits the trees, ground, bushes, animals, insects, and other things around them, it bounces around in all different directions. But, the bats are able to tell the direction or angle that the echo is coming back from. This lets the bat know the direction that things are. Now, since sound travels very fast, the bat is also able to tell how long the sounds take to come back to them. So, now the bat knows where the echos are coming from AND how far away things are. Since sound travels very fast, this all happens almost instantly, and since the bats also are very, very fast they are able to know exactly where they are while they are flying without using their eyes.
717949
They are "cold blooded."  Unlike warm blooded mammals like humans, flies and other insects do not produce their own heat.   They need to get heat from outside sources, like the sun or the air.  When it's cold, they move slower because their whole physiology has slowed down.
56198
If a tree falls in the forest when nobody is there, . . . does it make any noise? This is a complicated question, that seems simple. It makes a sound, which may or not be noise. Noise is sound that is unorganized, it requiers the presence of someone to make that determination. The same thing holds true for you, when you have somthing to say. In order to get someone to listen to you, someone has to be there listening. While you can't make anybody take the time to listen, there are things that will better your efforts at being heard. When a comic gets up to tell jokes, not everyone laughs. At times everybody laughs, and then there is the joke that dosen't get any response at all. You can take a few lessons from the comic. No, not about telling jokes, but rather about delivery. He has managed to speak to a wide audience. When you speak to large groups, your words will find some willing ears.\nMatt.
321389
flies are more maleable - impact resisitant\nbuilt better I guess\nthe mass and speed of the fly are a lot less\n\nbirds have necks with thin hollow breakable bones\nflies have a head and an abdomen and thorax but they have exo-skeletons
918346
that is an ancient question like Which came first, Chicken or Egg.  Nobody knows that answer for sure.\nI believe it does not make noise, as noise is something that is created inside the head which has ears that interpret the vibrations as sound.  No ears, no sound.\nClarkie's theory on Tree Noise.
61716
The air inside the vehicle is moving the same speed as the vehicle. To the fly it's still air, unless a window is open, then the fly may not be able to fly normally.
6433
The legs of a fly have a primary role of helping the fly to land and lift off, and also move about a little when its not flying. If the fly would not have wings, it would be able to move futher on its legs, but the mobility would be severly restricted because the legs haven't been used in that sense before. This fact is confirmed from experimentation done in around 2003, where a genetically mutated fly which didn't grow any wings tried to move solely on its legs.
786419
During the summer and autumn/fall, many fly species lay eggs in plants and things. The eggs hatch, and the larvae stay in the plant for the winter, developing into adults. In the spring they leave the plant and find a mate, and the cycle starts all over again.\n\nSome flies do not need to mate to reproduce, and their offspring are 'clones' of the mother. This is a very quick way of producing offspring, so the population increases very quickly when it becomes warm again.\n\nThe black flies you saw were probably lying dormant in some nooks and crannies somewhere. When the temperature drops, their body processes slow down and they 'hibernate'. When the temperature rises they become active again. Thats probably where you blackflies came from
1072685
Noise is created with the movement of particles.  The popping noise is caused by the air particles inside the balloon very rapidly moving outside the balloon.
74
There make very low frequency sounds that we cannot hear. They also make sounds that we do hear and it is because they what other animals to hear it.
1073680
What is sound? Air in motion. What is wind? Air in motion. If the air movement is high enough or vibrates at the right frequencies because of what it is passing through or around, we hear it. Most of the time, the intensity of the wind is too low to produce much sound audible to humans.
39901
Yes. It would be like saying things don't make sounds because deaf people can't hear it, It still makes sound, just no one is around to hear it.
1152245
If the fly flies in while the box car os still, the doors are shut and the fly doesn't land, the fly will move relative to the outside, not the train.  Once the fly lands, It will take the properties of the train as its frame of reference.  So, it will move around the box car as if it were still.\n\nIf the box car is open, you are "opening" the system, in that the box car is not it's own environment.  Turbulence, etc, will affect flight.
968219
you hear a noise because someone is making noise for people to laugh. you answered your own question.
1032013
Flies are among the fastest of all flying insects. The buzzing of a fly is the sound of its wings beating. A house fly's wings beat about 200 times a second, and some midges move their wings 1,000 times a second. House flies fly at an average speed of 4 and 1/2 miles (7.2 kilometers) per hour. They can fly even faster for short distances to escape their enemies, which include people and many birds.
442757
No, flies definitely don't lay eggs every time they land.  They lay their eggs in suitable locations, and even more importantly, only the female flies actually lay eggs, so about 50% of the flies that land on you will never, ever lay eggs under any circumstances.