Why does my ocarina have airy high notes?
Ocarinas can have airy high notes for a number of reasons, commonly dirt in the windway and not blowing hard enough. It's also a symptom of a badly designed ocarina; however, this is less common than it used to be. Ocarinas are naturally airy to some extent. This will be more noticeable to you as a player as you are close to the instrument. The airiness shouldn't drown out the note you are playing though. If it is, try some of the following points:
You may have run across the 'acute bend' from other sources, a technique which involves shading the ocarina's voicing against the chest. If so, I don't recommend using it.
I believe this is an acoustic effect that increases the perceived loudness to the player by bouncing sound off their chest into their ears. From what I've observed of others doing this in person, it makes little difference to an observer's perspective. It can sound worse as the sound coming from the voicing is directed downwards, away from the audience. I do not recommend using this technique for that reason; plus, it is ergonomically awkward and looks silly in a performance. Any ocarina that 'needs' this technique is a bad instrument.
The windway may be blocked
If your ocarina has suddenly become airy, this may be due to dirt in the windway; dirt can build up over time, and insects may also crawl into the windway. Any obstruction in the windway is a problem as it will create turbulence and increase airiness. You can clean the windway by folding a strip of paper and pushing it through. Note that wind-ways are normally much larger at the mouthpiece end than the voicing. If your paper gets stuck, reduce the number of folds—don't force it through. For larger obstructions, you would be better off pushing the paper through from the voicing end.
You may not be blowing hard enough
A very common reason that an ocarina will have airy high notes is because you are not blowing hard enough. As holes are opened, air can escape the chamber. To compensate for this, you must blow harder or the tone will become more and more airy.
The high notes will only sound good within a relatively small pressure range, so try fingering one of the high notes and vary your breath pressure, listening for the point that they have the cleanest sound. This is covered in more detail on the page 'Playing the ocarina in tune'.
You may be shading the finger holes
Even if a finger hole is open, there is a notable distance where the presence of a finger will 'shade' the hole, causing the ocarina to play flatter than it should. If you blow harder to compensate, the tone will sound more airy.
Watch yourself playing in a mirror and make sure you are not doing this. To check how the high note sounds under optimal conditions, play it it while holding the ocarina by its ends so no fingers are close to the holes.
You may be blowing into the windway at the wrong angle
How you blow an ocarina has a significant impact on the tone you get from the high notes. It's important to hold the ocarina so the air flows directly into the windway without a 'kink' at the lips as this creates turbulence. Keep your head up and hold the ocarina straight in front of you. Use a mirror to see what you are doing.
Your palm may be in the airstream
As you play higher notes, you blow harder. If this fast-moving air hits your left palm, it makes a noise. Consequently, you should keep your hand out of the air-stream when playing the high notes. If you're playing using the 3 point grip, an easy way to do this is to open the pinky hole by rotating the left hand from the wrist, pivoting on the index finger.
You may be creating turbulence with your tongue position
The position of your tongue has a large impact on tone clarity: raising the back of your tongue, or positioning its tip too close to the teeth results in a noisy tone. Keep the rear of the tongue at the base of the mouth at all times. The tip of the tongue should also rest at the base of the mouth, inline with the lip and covering the teeth, unless you are tonguing a note.
There is another valve in the thought called the glottis, which is the 'lid' that closes if you hold your breath with your mouth open. When playing the ocarina, the glottis should be fully open at all times as restricting this will also harm the high notes.
The ocarina may be fine, but...
Your perception of the instrument is not the same as your audience's
How an ocarina sounds to you differs from how it sounds to an audience. The high notes will sound more airy to you because the ocarina is only inches from your ears. This isn't a problem from the perspective of an audience. Wind noise is much less audible to someone listening from a distance. Also, ocarinas have irregular sound projection, and most volume goes directly forwards away from the voicing—and you by extension.
Because of this, I strongly recommend finding out how your instrument sounds as an observer. Get someone else to blow it—preferably using good technique—and have a walk around. You may be surprised by how different it sounds.
The sound you hear is affected by room acoustics
The ocarina's pure timbre is quite susceptible to an acoustic effect called comb filtering. The sound reflections inside a room may make certain notes sound stronger or weaker than they actually are. Try playing outside in a wide open space to get a true sense of how your instrument sounds.
Psychology is also a factor
If the ocarina is your first instrument and you suddenly notice the airiness, it may be a psychological effect. When you first play an instrument, everything is a conscious effort: your attention is saturated with multiple things like fingerings and breath control. As you spend more time playing music, these things become subconscious and, as this happens, you may pay more notice to what you actually sound like. Thus, you may suddenly notice things that were always there but you were not aware of. This is a good thing as it means that you are making progress.
The ocarina is airy by design
Some ocarinas are airy by design, such as those made by Fabio Menaglio. These ocarinas were designed to fill large music halls and have a large voicing to achieve a high volume. A side effect of this is it makes the sound more airy. This isn't a problem from the perspective of an audience. Wind noise is much less audible to someone listening from a distance.
Also, an airy timbre isn't always a bad thing, as it can be very effective for some types of music.
More holes equals more airy high notes
The more holes an ocarina has, the more airy sounding its high notes will tend to be. This is a side effect of the instrument's lossy physics. A 10 hole ocarina will generally have a cleaner sounding high end than a 12 hole, but this does depend on instrument quality. Multichambers are even better as the individual chambers only provide a small portion of the total range.
You have a badly made ocarina
If your ocarina was very cheap, there is a good chance it is poorly made and will never be able to play cleanly. If an ocarina's voicing is mismatched to its chamber or if the windway is rough, it will have poor sounding high notes. If you've tried all of these options, I'd get a better instrument and not skimp this time. Relative to other instruments, good ocarinas are not expensive. See 'Identifying playable ocarinas'.