Hello, everyone.

I picked up an Irish whistle while living in Ireland for a brief period. I unearthed it today and have been trying to get started.

My issue is, I can't seem to get a good quality sound when playing the following D: 0XXXXX.

It comes out either squawky or "breathy" if that makes any sense. If I maintain the same "air pressure" for the note as I use for the previous notes in the scale, it sounds breathy or weak. If I blow harder, it squawks. I've tried adjusting the angle that I'm breathing into the whistle, adjusting the mouth piece (trying to adjust the pitch), blowing softer/harder...

I'm not sure what's up with it. It could simply be that I'm "tune deaf" and it's the proper note. Any help would be great.

The mid-D with the top finger

The mid-D with the top finger open can be tricky for some instruments -- can you get a decent 2nd D with the finger down? If so you may just have to play it that way. There could be a problem with the fipple (dirt, warping, deformation, etc.) that would cause the problem as well. Do you know what brand of whistle it is?

You might want to spend a few

You might want to spend a few bucks and try a better whistle. I highly recommend a "Generation" (brass) in the key of D. If you feel really wealthy, you might want to spend a bit more and get a tweaked whistle. It's a good investment provided that you stick with playing the whistle. The reason that I suggest a tweaked whistle is that most whistles are mass produced now a days and they are not what they were in days gone by. Although manufacturers try, most whistle players will tell you that only (my guess) one out of twenty whistles really is a great whistle.
I also strongly suggest that you check the tuning on your whistle. The length that the mouthpiece is seated on the body can greatly affect its playability. Is your Whistle tuneable? If its not, (chances are) you may be able to make it a tuneable whistle by simply sticking the head in some fairly hot water, and while using a towel to prevent burns, and while hot, quickly loosen and remove the mouthpiece (fipple). Pre-marking its location before heating is a good idea. Of course, you will need to tune it up once you get the mouthpiece removed. This simple process can make life much easier for you. A keyboard or even an app (if you have a iPad/touch) works great.
Freeman whistles.com sells a great tweaked whistle for around $25.00. I own 3. I absolutely love them all. Good luck, and keep playing!

Rich