NASA microphone detects turbulent invisible air

The sudden turbulence sometimes experienced when flying is called clear-air turbulence, so named because there are no visible clouds or atmospheric features to warn of the disruption.

Turbulent invisible air can seemingly come out of nowhere and wreak havoc on aircraft.

Researchers Qamar Shams and Allan Zuckerwar at NASA's Langley Research Centre in Hampton, Virginia, began developing something that could find the turbulence zone hundreds of kilometres away.

They knew that everything in the atmosphere can make a sound.

Volcanoes rumble, waterfalls crash, and air rushes, but there is more to that sound than what our ears perceive. Much like how infrared light consists of frequencies that are not visible to the open eye, there is an audio analogue called infrasound.

Infrasound consists of pitches too low to be heard by the human ear, between 0.001 and 20 hertz.

Began in 2007, the NASA researchers experimenting on something that could listen to these low frequencies in high fidelity.

As microphones use a moving diaphragm to pick up audio where sound waves, Shams and Zuckerwar experimented on such microphones with low-tension diaphragm and a wide radius paired with a large, sealed air chamber behind it. The experiments allowed the microphone to hear ultralow sound waves that travel great distances.

And now, such infrasonic microphones are manufactured by PCB Piezotronics of Depew, New York, under contract with Langley, Into-Asian News Service (IANS) reports.

The new kind of device is now on trial.

One of the trials found that the microphone was able to pick up and locate atmospheric turbulence more than 300 miles away, in the skies above Pennsylvania while it was placed in an equidistant triangular pattern around the grounds of Langley's runway, IANS reports.