I'm 15 years old and started to learn the flute through school last month. I'm having some trouble on getting pure flute tone, my notes sound airy. Do you have any tips on how to improve? I really want to be a good flute player!!
That's great that you just started playing the flute! :) It takes time to develop a pure, clear tone, so it's perfectly natural that you're finding that your notes are sounding airy right now.
The key to flute tone is your embouchure (the position of your lips when you play). How your lips are positioned affects how airy or pure your tone will be, so here's some tips on developing a clear sound:
Creating your embouchure:
For most people, the aperture between your lips will be more of a slit than a round opening. Think of other instruments like the oboe, clarinet, trumpet, etc... for these instruments, air gets channeled into very small mouthpieces or reeds. It's the same for the flute - we don't have a mouthpiece to blow into, but our lips are our mouthpieces, and we channel the air through a very thin aperture. The exact shape and size depends partly on the shape and size of our lips - for each person, it's going to be a little different, so you'll have to experiment to see what shape sounds best for you.
Positioning the flute on your chin
: How you align the flute on your chin against your lower lip can also affect your sound. Try positioning the flute so the edge of the hole on the lip plate lines up approximately with the edge of your lower lip (where the color starts). This means that a little bit of the hole in the lip plate will be covered by your lip - that's okay, as long as it's not more than about 1/3. If the hole gets covered too much, the sound will be muffled and flat. If not enough is covered, the sound will be harsh and sharp.
Focusing the airstream
: Your airstream - the air your blow to make a sound - should be very, very focused and compact. The more scattered and diffuse your air is channeled, the fuzzier your sound will be. Blow across the embouchure hole so a little air goes down into the hole and the rest splits across - this is what creates the sound. Your embouchure should be firm, but not pinched or strained. It's similar to the way we blow across a bottle or on a hot spoonful of soup, but there needs to be more control and firmness in the lips to enable the airstream to have the compact solidity it needs for a clear sound.
Experiment with your embouchure
: Everyone's lips are unique, so it'll take some experimentation to see what creates the best sound for you. Try firming your lips, because if they're too loose, the sound will be airy. (Too tight, and you'll pinch off the sound, though.) It often helps to watch in a mirror as you play and try some different things, so you can see what you're doing if anything really helps. Also, experiment with the size and shape of your aperture: again, remember that it's probably going to be more of a narrow slit than a round hole, because this lets us concentrate the air, rather than spewing it all out in all directions.
Check the angle of your flute
: Make sure that the flute is aligned parallel to your lips and isn't slanting away from your mouth. Flutists often develop "band posture" due to cramped seating conditions, and if the flute angles sharply away from your mouth, so the air isn't passing evenly across it, then this can affect the sound. You don't have to hold your flute exactly parallel to the floor (very tiring!), but your head should tilt slightly to follow the angle of the flute so your flute stays evenly placed on your chin. (Too much tilting of the head, and your air won't flow right, though.)
Check that the flute's keys are sealing tightly
: If you notice that only a few notes are fuzzy, or are a lot fuzzier than the others, then one or more of the flute's pads may not be sealing properly. If this is the case, and if your flute hasn't had a checkup at your local music store / repair shop lately, then this could be a factor. Student flutes can come in all kinds of conditions, but hopefully yours is in good shape. :)
Long tone practice
: I know you've got a lot to think about right now with holding the flute and learning fingerings as well as making a sound, so it'll help if you practice your tone just like you practice technique. Set aside a few minutes of each practice session to play some long tones - take a deep breath and hold one note out as long as you can. As you play, concentrate on getting a clear, focused, solid tone, and try various subtle changes to your embouchure to see what helps and what doesn't. Use this time to experiment and develop your tone without the distraction of fingerings and rhythms.
Finally, since you're just starting out, this link on my website may provide some useful information on holding & assembling the flute: http://silentgalaxy.com/images/Flute_Assembly_and_Posture.pdf
I hope this helps you with developing your sound. It's great that you're so eager to improve, and it sounds like you're going to be a thoughtful, conscientious flutist. Have fun with the flute! :)