I noticed this awesome whistling effect last week when rinsing our stainless perforated coffee filter (1/n)

The filter consists of a simple perforated stainless disc spot welded into a cup. It’s not under any particular tension. Scale is cm. (2/n)

The effect is not dependent on the aeration of the water stream. The wavelength seems tied to the speed of the stream. The angle that gives the highest amplitude is ~30 degrees from the stream vector. (3/n)

I’m thinking of working on some ideas to explain this before looking it up, and also maybe ordering various perforated metal sheets from @McMasterCarr and a couple nozzles to play with. (4/n)

But, somebody may be able to illuminate this effect and entertain us all, saving me time and money...??? (5/n)