Jet Whistles on the flute can be amazingly effective, but one has to compose them with care. You can hear a sound file here on Mats Möller’s website. He calls it “Strong air stream without tone”. Two composers who use jet whistles effectively in ensemble situations are Helmut Lachenmann (Mouvement, Zwei Gefühle) and Bernhard Lang ( DW 9 Puppe/Tulpe) –  you might want to check out their notation and usage.

A few basic pointers:

• Jet whistles need time to set up. The flutist has to go from normal playing position to inserting the entire lip plate into his or her mouth.. (insert dirty joke here…) You can sorta, kinda do it with the lips just covering the hole instead of the whole lip plate, but it doesn’t have the impact. To be on the safe side, make sure there is a rest before and after the jet whistle.
• A jet whistle is a quick blast of air that can begin with an ascending pitch or a descending pitch. Graphically they can be /, \, /\.
• Quick is the operative word here, especially if you want something that will carry in an ensemble situation. I have been asked to do slow ones, which are possible if you don’t need a high pitch at the peak and if you don’t need to project the sound. In other words, it has to be a quiet environment. I would even go so far as to argue that what I would be doing in this situation is colored air noise, and not a proper jet whistle.
• It is not possible, in my experience, to notate the exact resultant pitches. A graphic representation is the nicest way to go about it.
• Jet whistles are most effective on the C flute, and less so on piccolo, alto or bass. One can make whooshing sounds and all kinds of colored air noises in these flutes, but for whatever acoustical reasons, a true and dirty jet whistle doesn’t have the same impact on these flutes. Some alto and bass flute can produce a decent jet whistle, but you need a very sharp blowing edge on the headjoint. Only a small handful of my colleagues with Brannen Kingmas and Kotatos can do them well.
• I mentioned the piccolo, and would like to add that piccoloists with headjoints out of quality wood are not going to want to subject their embouchure holes to the enzymes from saliva. Putting your mouth on the instrument is a quick way to devalue it. The embouchure cut is very precise on a piccolo, the smallest changes to the blowing edge can make a big difference.  The instrument is difficult enough without degradation to its blowing edge.

Any flutists out there with any thing to add?