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How do noise cancelling headphones work?

Science
Can you draw better than a 40,000 year old? Ancient cave drawings in Indonesia are as old as famous prehistoric art in Europe. Our ancestors were drawing all over the world 40,000 years ago, according to a study. And it hints at an even earlier dawn of creativity in modern humans than scientists had thought. Ar... - Posted on October 13, 2014
How do dolphins sleep without drowning? Dolphins aren't like fish, which can breathe underwater. They're mammals and they have to get to the surface to breathe air periodically. And a lot of them – like everyone's favorite, the bottlenosed dolphin – can only hold their breath for seven minutes or so.... - Posted on October 2, 2014
Colossal squid is as long as a minibus! It was a calm morning in Antarctica's remote Ross Sea, during the season when the sun never sets, when Capt. John Bennett and his crew hauled up a creature with tentacles like fire hoses and eyes like dinner plates from a mile below the surface. A colossal squid: 770 pounds,... - Posted on September 19, 2014
Why do bugs die on their backs? Well, they don't all die that way. But many succumb to the laws of physics in their final moments. It's at that point that normal blood flow stops, the legs contract, and the bug gets top heavy. Inevitably, it falls over onto its back. Of course, a stiff breeze or a curious... - Posted on September 18, 2014
Why do songs get stuck in our heads? Ah, yes, the evil ear worm, which sometimes has our hearing seemingly sticking on the same song, over and over. Polls show that a stunning 90% of us have experienced these hearing parasites and nine out of 10 report having them at least weekly. Who remembers these classic ... - Posted on September 16, 2014
“Dreadnoughtus” dwarfs 7 elephants Researchers studying the remains of a dinosaur that was bigger than seven bull elephants. The scientists have given it an equally colossal name, Dreadnoughtus, or "fearing nothing." Scientists hope its unusually well-preserved bones will help reveal secrets about some of the... - Posted on September 7, 2014
Does music make you smarter? The founder of an organization that provides free music lessons to low-income students from gang-ridden neighborhoods has noticed a hopeful sign. The kids were graduating high school and heading off to some big universities. That's when Margaret Martin asked how the children... - Posted on September 5, 2014
Puffins in peril – want to help? Wanted: puffinologists. No experience necessary. The Audubon Society wants bird lovers to contribute research to a project. Scientists hope it will help save Atlantic puffins from starvation in Maine. There are about 1,000 pairs of the seabirds, known for their multi-... - Posted on August 6, 2014
If you were a crab, what color would you be? A rare blue-colored red king crab has been caught. Frank McFarland found the crab in his pot July 4. The crab is being kept alive at the Norton Sound Seafood Center. People show up to have their photos taken with it. Scott Kent, with the Alaska Department of Fish and... - Posted on August 5, 2014
How do noise cancelling headphones work? Just by covering your ears, headphones help block the sounds around you. But active noise cancellation takes a little bit more work. Different sounds have different waveforms. And a microphone on noise cancelling headphones registers the waveforms coming from the sounds aro... - Posted on June 13, 2014