Today’s Wonder of the Day was inspired by Mrs. Boles' Class. Mrs. Boles' Class Wonders, “Why does the wind whistle?” Thanks for WONDERing with us, Mrs. Boles' Class!
One of the unique things about wind is that you can't really see it. Sure, you can see the effect it has on objects, but you can't really see the wind itself.
Think about it. How do you know it's windy outside? If you gaze out the window, you might notice a flag waving or tree branches . These things are being moved by the wind, but you still can't see the wind itself.
If you listen carefully, though, you might be able to hear the wind. Depending upon the speed of the wind and the objects it's passing through, around, or over, the wind can cause a wide variety of sounds, from the soft rustling of leaves and the delicate notes of wind chimes to the "whoosh" of a stiff breeze and the loud whistle of storm winds approaching.
How does wind make all those different sounds? To get to the bottom of this mystery, we need to remember exactly what sounds are. The sounds we hear are actually pressure waves that travel through the air to our ears, where they are converted into electric signals that our brains interpret as sounds.
You can think of sounds as vibrations that move through the air and make your ear drums vibrate at frequencies that your brain can decode as particular sounds. Since sounds move easily through the air, it's easy to see how wind can produce so many different sounds.
Take trees, for example. They're like natural instruments for the wind to play. As the wind passes through and around their branches and leaves, they cause those objects to move back and forth. This movement creates vibrations in the air, known as longitudinal pressure waves, which can travel to your ears as soft rustling or louder whooshing sounds.
As wind picks up speed, it can cause objects to vibrate even faster. The faster an object vibrates, the higher the pitch will be of the sound created. This is why you may hear the wind create a high-pitched whistling sound when it passes by certain objects.
When you think of the wind passing by all sorts of objects on the face of the Earth, there's virtually no limit to the range of sounds it can create. The next time you're outside on a windy day, take some time to listen closely to the sounds the wind makes. You never know what you'll hear!