Jet turbulence noise shifts from high to low frequencies as eddies decay downstream

Evidence

Faster jets (higher Reynolds number, > 10, 000) are very turbulent, with a wide spectrum of sound emanating from the jet. At lower Reynolds numbers, the eddies are larger, less frequent, and give rise to noise that emphasizes lower frequencies. … As you move your hand farther away, notice how the turbulent eddies becomes less violent and much lower frequency. This is a natural degradation process of jet turbulence as it evolves from its source. — Eric J. Heller, Why You Hear What You Hear- An…, 1336

Categorization

• XREF: Connects to the turbulence-frequency relationship in whirls and eddies discussions from earlier in the book.