Owl flight is not magic silence; measurements show the big win is hiding which sounds?

Answer: High-frequency flight noise

High-frequency flight noise ✓ — Right. Several measurements and reviews point to owl wings especially reducing higher-frequency flight noise, including ranges above about 1.6 to 2 kHz. That is a more useful trick than simply lowering total volume: it removes the sharp cues that prey and the owl's own hearing system are likely to notice. The surprise is that silence can mean spectral reshaping, not zero sound.

Low-frequency wing hum — Low-frequency sound is not where the cleanest owl advantage usually appears. Some measurements found owl gliding noise concentrated lower than duck noise, but comparisons with hawks and kestrels show a stronger reduction at higher frequencies. This matters because many prey-hearing cues and masking problems sit in kilohertz ranges. Owls are quiet, not physically soundless.

All flight noise equally — All-flight-noise reduction is the intuitive cartoon version, but measurements point to a more selective spectral story. Owl flight can remain physically audible while losing the higher-frequency cues that matter most for detection and masking. That distinction is useful: quiet design may target the most revealing frequencies rather than flatten everything equally.