Ok so the overall length of the whistle is 2 1/2inches.
If your print matches that try the fallowing:
Cover one of the ports on the sides with the palm of your hand. (Try to completely cover the opening to stop airflow.)
While one side is blocked blow as hard as you can into the whistle.
Repeat with other side.
If you still get no sound from either side check for for blockages. Let me know and I can tell you what to look for.
If you get both sides to whistle on their own try uncovering both sides, take a deep breath and blow as hard and fast as you can. You do have to blow hard but when you do it gets quite loud. If it still doesn't whistle their may be something restricting airflow somewhere.
The solution either way may be to try to the print again. But I am happy to help narrow down the issue. "solid_liq" in his comment had success with supports. If bridging is an issue you could try that but it was designed to be within the bridging abilities of most printers.
Hope this helps! Keep me in the loop, I want to get it working for you.