vacuum cleaner does not produce vacuum,actually it produce a suction effect for which heavy capacity motors are required and they produce loud sound.
That would be the motor you are hearing, which is not in vacuum. Good play on words though. Take it up to space and you won't hear a thing ;-)
Actually, a vacuum cleaner does not produce a real vacuum. It -pulls- air into a chamber by use of a noisy electric motor. Even if a vacuum were created in the collection chamber, you would still hear noise produced by the motor which is situated outside the vacuum chamber.
Some comments: Vacuum literally means, a space containing nothing. Vacuum in that sense does not exist inside a vacuum cleaner, but then it also doesn't exist anywhere else in the universe either. A vacuum cleaner produces what is often called partial vacuum (i.e., a region of lower-than-atmospheric pressure.) It is the wind rushing into that partial vacuum that picks up the dust out of your carpet and carries it to the filter bag. The higher the vacuum, the less sound will be able to propagate through it, but as other posters have already pointed out, the machine is not in the vacuum, the vacuum is in the machine. The noise that you hear does not come from the motor. If you pulled the electric motor out of a vacuum cleaner and plugged it in to the wall, the most you would hear would be a gentle hum. The noise mostly comes from the BLOWER---the metal blades attached to the motor that move the air. If it were designed by an aeronautical engineer, then the blower might not make much noise either, but it wasn't. It was designed by some hack copying a design that worked well enough for someone before. The noise mostly comes from turbulence created behind the blades as they move through the air. More noise is created by turbulence in the wind that rushes up the pipe and into the bag.
The sound from a vacuum cleaner comes from it's motor. That sound travels through the air around the cleaner to you, never having anything to do with the actual vacuum inside the cleaner.
