It sounds like a high frequency note going to a low frequency note, with a good amount of reverb.
Now, what makes the notes?
Maybe not quite right, but it could be done with a small drum, 8" perhaps.
You hear the bottom head first, so tune that to the high note.
Then you hear the top head, so tune that to the low note.
Normally, both heads would be tuned the same, to make it resonate.
Adding reverb is easy.