dear folks,
i'm looking for a component (motor?) that outputs air (like a small reverse vacuum-cleaner) if it is triggered. does anybody know of anything like this exists?
sorry for the terrible explanation – if i'd know better keywords i could probably google 
Like an air pump?
CrossRoads:
Like an air pump?
yes! only smaller and faster. and somehow connectable to an arduino.
Can you clearly explain what you actually want to do?
i'd like to play a flute/recorder with an arduino
Depends on pressure and volume required.
Lots of different air pumps for different applications.
Fan = low presssure high volume.
Compressor high pressure medium to high volume.
Vane pump somewhere between those above and a diaphragm (aquarium) pump.
bennii:
i'd like to play a flute/recorder with an arduino
Vane pump.
Fan could be used but expect a large power requirment
Vane pumps can be found in gas sampling equipment if you can find one.
A large diaphragm pump may work but an accumulator would be required to smooth out the pulses.
Organs use a fan blower but they are probably too large and in any case require mains.
Boardburner2:
Vane pump.
hehe, thanks.. just started to ask you. i have absolutely no clue about this stuff – have you got any experience with vane pumps? or possibly a blind guess pointing me in the right direction as for what to buy?
The air pump has nothing to do with Arduino.
The hard problem will be to have the Arduino open and close the holes or valves in the instrument.
bennii:
hehe, thanks.. just started to ask you. i have absolutely no clue about this stuff – have you got any experience with vane pumps? or possibly a blind guess pointing me in the right direction as for what to buy?
Possibly an old refrigerator pump, they are normally dicplacement pumps but can be had cheaply, if you can find an obliging scrapyard, EU regs makes this difficult these days.
If you can find a suitable pressure regulator an old car tyre may do, i use one for my airbrush when its late.
One of those matress pumps would probably work but it will be noiser than your flute
jremington:
The hard problem will be to have the Arduino open and close the holes or valves in the instrument.
i was considering a "blechbuegelmagnet" or "hubmagnet" (don't know the english term) as such: 
i suppose it'd be lots and lots of trying around, how ever the pumping-part is currently my main concern. i'd be gracious for any further ideas and hints
Solenoid works, i have seen this done on a clarinet.
I suspect that some work would be needed to get rid of the rather annoying clicks though.
Boardburner2:
Possibly an old refrigerator pump, they are normally dicplacement pumps but can be had cheaply, if you can find an obliging scrapyard, EU regs makes this difficult these days.If you can find a suitable pressure regulator an old car tyre may do, i use one for my airbrush when its late.
oh jee.. i'd have no idea how to get something as such to work to my desire. so – am i getting you right, that it'll be hard to find a prebuilt part for the pumping?
Boardburner2:
Solenoid works, i have seen this done on a clarinet.
I suspect that some work would be needed to get rid of the rather annoying clicks though.
that sounds incredible! glad to heat that it had worked for you.. googling "solenoid" doesn't make me all too smart. you possibly have a picture (or link) of the particular part that you used?
All kinds options there.
Likely will need to have a transistor between Arduino pin and solenoid coil to open the valve as Arduino output is only capable of 25-30mA from a 5V source.
incredible! thanks so much guys. i'll most probably be back, soon (:
bennii:
that sounds incredible! glad to heat that it had worked for you.. googling "solenoid" doesn't make me all too smart. you possibly have a picture (or link) of the particular part that you used?
I did not make it.
A clarinet already has pads to cover the holes so an ordinary solenoid to press the keys was all that was required i think.
You need about 10 litres per min at about 1 psi i guess.
Looking around that's fairly tricky to achieve, most sample pumps are diaphragm and .5 l/s.
I have similar to one of these
http://www.zefon.com/store/zefon-high-volume-rotary-vane-pump.html
If you can afford, they are very hard to come by second hand but i was lucky, old dentists surgery.
A fair few people have hacked refrigerator motors for airbrushing and they are very quiet so that is probably your best bet.
It's probably best to get the air supply sorted before you waste time on the rest.
Best i could suggest from new would be a diaphragm airbrush compressor and a bellows with a weight on to take out the pulses.
possibly using a gas low pressure regulator.
Good luck finding a quiet air pump!
Something like a voice-coil actuator pressing on a piston or airbag might be one way to control
air pressure quickly without much noise.
No worries, just turn the amp up to 11!
Maybe a servo pushing an arm into the airflow to deflect it away from the flute opening is all that is needed.
No clicking that way, just a little whir as the servo moves a few degrees.
Boardburner2:
A clarinet already has pads to cover the holes so an ordinary solenoid to press the keys was all that was required i think.
The holes under your three middle fingers on each hand have no pads on a clarinet or flute. That's because the plebian clarinet and flute players can't afford as many pads as their saxophone overlords can.
For an air solenoid I'd suggest the mini ones like those used in coffee machines. If you do go with an industrial air solenoid like those that CrossRoads linked make sure it's a direct acting ("standing up") rather than pilot operated ("laying down"). The latter has a minimum air pressure it will work with and that pressure will be much higher than the ~1PSI you'll want.