An interesting fact is that this has influenced the design of computer fans: <a href="https://news.softpedia.com/news/Lenovo-Details-Its-Unique-Owl-Wing-Cooling-Technology-Found-in-ThinkPad-Laptops-433893.shtml" rel="nofollow">https://news.softpedia.com/news/Lenovo-Details-Its-Unique-Ow...</a>
Here's the sound of owl flying: <a href="https://www.youtube.com/watch?v=d_FEaFgJyfA" rel="nofollow">https://www.youtube.com/watch?v=d_FEaFgJyfA</a>
That may be true from afar. But not when they fly by very near your head. They (some Owls, unlikely Barn Owls because of darker colors) startled me several times walking in the evenings or night, coming from somewhere above and behind me, diving into some garden or park, producing a strong <i>whooosh</i> about half meter away, then a short squeak/shriek, and lifting off with something mouse/mole/rat-like in its claws.
Similar discussion, which also contains one of the funniest comments I've seen on HN: <a href="https://news.ycombinator.com/item?id=23248779" rel="nofollow">https://news.ycombinator.com/item?id=23248779</a>
An interesting observation from this line of work (based on other articles in the area): the silence of owl flight depends on the frequency of the sound. Mice have a range of frequencies that they can hear. If you line up the two curves, you can see evolution in action. Owl flight becomes quieter just at the low end of the sound frequency that mice can hear.
BBC nature video about silent owl flight. Flight and audio comparisons of owls and some other birds.<p><a href="https://youtu.be/d_FEaFgJyfA" rel="nofollow">https://youtu.be/d_FEaFgJyfA</a>