Inexpensive and easy to build, these data-collecting balloons capture low-frequency sound in the Earth’s atmosphere.
Imagine if sending your science experiment 70,000 ft in the air just took painter’s plastic, tape, a dash of charcoal dust, and plenty of sunlight.
Daniel Bowman of Sandia National Laboratories presented his findings on using solar-powered hot air balloons to eavesdrop on stratospheric sounds at the 184th Meeting of the Acoustical Society of America.
The stratosphere — the second layer of the atmosphere of Earth, located above the troposphere and below the mesosphere — is a relatively calm layer of Earth’s atmosphere. Rarely disturbed by planes or turbulence, microphones in the stratosphere pick up a variety of sounds unheard anywhere else. This includes natural sounds from colliding ocean waves and thunder, human-created sounds like wind turbines or explosions, and even sounds with unknown origins.
To reach the stratosphere, Bowman and his collaborators build balloons that span 6 to 7 meters across. Despite their large size and data collection capability, the balloons are relatively simple.
“Our balloons are basically giant plastic bags with some charcoal dust on the inside to make them dark. We build them using painter’s plastic from the hardware store, shipping tape, and charcoal powder from pyrotechnic supply stores. When the sun shines on the dark balloons, the air inside heats up and becomes buoyant. This passive solar power is enough to bring the balloons from the surface to over 20 km (66,000 ft) in the sky,” said Bowman. “Each balloon only needs about $50 worth of materials and can be built in a basketball court.”
The researchers collect data and detect low-frequency sound with microbarometers, which were originally designed to monitor volcanoes. After releasing the balloons, they track their routes using GPS – a necessary task since the balloons sometimes sail for hundreds of miles and land in hard-to-reach places. But, because the balloons are inexpensive and easy to construct and launch, they can release a lot of balloons and collect more data.
Along with the expected human and environmental sounds, Bowman and his team detected something they are not able to identify.
“[In the stratosphere,] there are mysterious infrasound signals that occur a few times per hour on some flights, but the source of these is completely unknown,” said Bowman.
Solar-powered balloons could also help explore other planets, such as observing Venus’ seismic and volcanic activity through its thick atmosphere.
Meeting: ASA 184th Meeting
I think that the sound can came from the baloon.
the pyramids are using sound waves to not only transmit our location,but also as a power house to energize portals. Hmmmmm,how about that.The more they dig out the Bosnia pyramids the more energized they are becomming. Unfortunately this system is now obsolete,its a proven fact that sound waves can be modulated to travel faster the light speed
Bob, you are something special indeed
Bob – you are something special indeed. I’m going to don my tinfoil hat ASAP.
It still sounds like sounds of movements of the materials of the balloon to me. Just because it’s in the low infrasonic range doesn’t mean it’s not coming from the balloon itself, just lower/slower movements of the material that are not in the human hearing range. I don’t know why that would be that big of a surprise given the winds moving the balloon around in the Stratosphere.
I would like to have the pdf file of the publication in
J. amer. acoustical society
THANKS in advance