A free jet generates periodic vortices without any resonator

Evidence

Like the von Kármán vortex street behind an obstruction, a free jet, such as the sheet of air coming through a window cracked open slightly, will often generate vortices at a regular rate, if the Reynolds number is in the right range. No resonator is necessary. — Eric J. Heller, Why You Hear What You Hear- An…, 1313

Categorization

• XREF: Directly relevant to the reader’s why-do-we-hear question: establishes that resonators are optional for vortex-based sound generation.