快猫短视频

YOU CAN鈥橳 hear it, which may be a good thing. Infrasound has a frequency below the lower limit of human hearing (about 20 hertz), and is emitted by just about every turbulent natural event on Earth, and some unnatural ones. If we could hear it, we鈥檇 be subject to a constant cacophony.

If it isn鈥檛 audible, can it tell us much? Yes indeed. Acoustics researchers have monitored infrasound waves for over a century. During the 1950s and 1960s, infrasound sensors were used to track atmospheric nuclear tests, and now a global network of 60 sensors is being built to help police the UN Comprehensive Test Ban Treaty. 快猫短视频s are excited because the network will also provide useful data about natural atmospheric phenomena.

Such as? One of the most intriguing prospects is analysing the build-up of severe weather systems such as hurricanes and predicting their development. One part of the network will be an infrasound station at Cape Verde off Africa鈥檚 west coast, where hurricanes take shape before heading to the US. Researcher Michael Hedlin of the Scripps Institution of Oceanography at the University of California at San Diego hopes to hear 鈥渆xtremely low-frequency signatures鈥� from the storms.

So what other natural phenomena make infrasound waves? The movement of tectonic plates, avalanches, exploding meteorites and volcanoes, as well as the northern lights, where charged particles in the air cause atmospheric gases to heat and expand. And animals such as elephants may use them to communicate.

But do humans sense them at all? Quite possibly. Some experiments show that low-frequency sounds give people weird sensations (shivers down the spine and so on). Could this explain the feelings people report in houses believed to be haunted?