Tag: acoustics

Fluids Round-up
Time for another look at some of the best fluids content out there. It’s the fluids round-up – with a special focus this week on oceans!
– Ryan Pernofski spent two years filming the ocean in slow motion with his iPhone to make the short film “Slowmocean” seen above. It’s a gorgeous ode to the beauty of breaking waves.
– Oceans with higher salinity than Earth’s could drive global circulation that would make exoplanets more hospitable to life.
– Speaking of alien oceans that could harbor signs of life, there’s discussion afoot of how future missions to icy moons like Europa or Enceladus could collect samples from plumes ejected from beneath the ice.
– Wind and waves make harsh, erosive environments. This photo essay from SFGate shows how greatly the sands of Pacifica shift over time. (submitted by Richard)
Bonuses:
– New research explores how Martian mountains may have been carved out by the wind.
– Ever listened to an orchestra made from ice? You should! Learn about Tim Linhart, who builds and maintains ice instruments. (submitted by ashketchumm)
– MIT has demonstrated a new 3D-printing technique that allows for printing liquid and solid parts simultaneously, allowing would-be creators to rapid-prototype hydraulically-driven robotics.
Even more bonus bonus!
– ICYMI, the new FYFD video made Gizmodo!
If you’re a fan of FYFD, please consider becoming a patron. As a bonus, you’ll get access to this weekend’s planetary science webcast!
(Video credit: R. Pernofski; via Flow Visualization; Pluto image credit: NASA/APL)
April 14, 2016
Fluttering Feathers
Birds do not always vocalize in order to make their songs. The male African broadbill, shown in the top video above, makes a very distinctive brreeeet in its flight displays, but as newly published research shows, the sound comes from its wings, not its voice. During the display, the broadbill spreads its primary feathers and sound is produced on the downstroke, when wingtip speeds reach about 16 m/s. By filming a broadbill wing with a high-speed camera in a wind tunnel at comparable air speeds, researchers could localize the sound production to the 6th and 7th primary feathers.
In the second video above, you can see these feathers twisting and fluttering in the breeze. This is an example of aeroelastic flutter, a phenomenon in which aerodynamic and structural forces couple to induce oscillations. The same phenomenon famously caused the collapse of the Tacoma Narrows Bridge in 1940. In the birds, however, the flutter is non-destructive and the vibration produces audible sound which the other feathers modulate into the calls we hear. Broadbills aren’t the only birds to use this trick; some species of hummingbirds use flutter in their tail feathers during mating displays. (Video, image, and research credits: C. Clark et al.; additional videos here)
April 6, 2016
Fluids Round-Up
Time for another fluids round-up! Here’s some of the best fluid dynamics from around the web:
– Band Ok Go filmed their latest music video in microgravity, complete with floating, splattering fluids. Here they describe how they did it. Rhett Allain also provides a write-up on the physics.
– Scientists are trying to measure the impact of airliners’ contrails on climate change. (pdf; via @KyungMSong)
– Researchers observing the strange moving hills on Pluto suspect they may, in fact, be icebergs.
– The best angle for skipping a rock is 20-degrees. Related: elastic spheres skip well even at higher angles. (via @JenLucPiquant)
– Fluid dynamics and acoustics have some fascinating overlaps. Be sure to check out “The World Through Sound” series at Acoustics Today, written by Andrew “Pi” Pyzdek, who also writes one of my favorite science blogs.
– Over at the Toast, Mallory Ortberg explores the poetry of the Beaufort wind scale.
– Could dark matter be a superfluid? (via @JenLucPiquant)
– Understanding the physics of the perfect pancake is helping doctors treat glaucoma. (submitted by Maria-Isabel)
– Van Gogh’s “Starry Night” shows swirling skies, but just how turbulent are they? (submitted by @NathanMechEng)
– The physics (and fluid dynamics!) of throwing a football – what’s the best angle for a maximum distance throw? (submitted by @rjallain)
(Video credit: Ok Go)
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February 18, 2016
The Inverted Glass Harp
You may be familiar with the glass harp, the instrument created by rubbing the rim of a partially-filled wine glass. But did you know that you can create the same effect by immersing an empty glass in water? In this video, Dan Quinn explains the physics behind both types of glass harps and why the pitch changes as you add or remove water. Vibration is the driving factor (as with most sound), and the key to the shifting pitches has to do with the change in mass of the material being vibrated. For more great physics, also be sure to check out Quinn’s previous video on tears of wine. (Video credit: D. Quinn)
September 16, 2015
Alligators Water Dancing
Amorous alligators call to mates with a behavior known as water dancing. Their audible bellows are accompanied by infrasonic sound–vibrations below the 20 Hz limit of human hearing. These vibrations from their lungs excite Faraday waves in the water near the alligator’s back and make the surface explode in a dance of jets and atomized droplets. I’ve seen similar results in other instances of vibration, but this may be the only example of this I’ve seen in the wild. Researchers studying the phenomenon noted that the frequency of sound the alligators emit corresponds to a wavelength equal to the spacing of the raised scales, or scutes, on the alligators’ backs. They hypothesize that the shape of the scutes helps males create the display. (Image credit: N. Marven, source; research credit: P. Moriarty and R. Holt; h/t to io9)
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July 22, 2015
How Loud Can Sound Get?
Sound and acoustics often intersect with fluid dynamics. Most of the sounds we experience are pressure waves traveling through air. In this video, Joe of It’s Okay To Be Smart takes a closer look at sound: what it is; how we measure it; and just how loud a sound can get. For air at sea level, the loudest possible sound is 194 dB. Add any more energy and it distorts the pressure wave from what we recognize as sound into what’s known as a shock wave. (Video credit: It’s Okay To Be Smart/PBS Digital Studios)
May 13, 2015
Extinguishing Fires With Sound
Engineering students from George Mason University have built a fire extinguisher that uses sound to put out flames. Since sound waves are mechanical pressure waves, they can move the air surrounding a burning material. Through trial and error the students found the high-frequency sound had little effect, but at frequencies between 30-60 Hz the sound waves could jostle enough oxygen away from the flame to extinguish the fire. They’re hoping the solution is scalable and can be applied to larger fires. For other wild ideas for chemical-less fire extinguishers, check out how researchers put out fires with explosions. (Video credit: George Mason University; submitted by @isanaht)
May 11, 2015
Popcorn Popping
The familiar popping behavior of popcorn is the combination of several events. When heated, unpopped kernels act like pressure vessels, managing to contain their boiling water content until a critical temperature of 180 degrees Celsius. At this temperature, nearly all kernels fracture. Popcorn’s jump doesn’t come from the fracture, though. Most of its acrobatics occur when a leg of starch branches out of the popping kernel. The starch acts somewhat like a muscle – after being compressed against the ground, it springs back, propelling the corn upward. Finally, by synchronizing high-speed video and audio recordings of popping corn, researchers determined that the pop in popcorn is not caused by fracture or rebound but instead is the result of the release of water vapor. (Image credit: TAMU NAL, source; research credit: E. Virot and A. Ponomarenko; submitted by Chad W.)
March 4, 2015
Making a Bottle Resonate
If you’ve ever blown across the top of a bottle to make it play a note, then you’ve created a Helmholtz resonator. Air flow across the top of the bottle causes air in and around the bottle neck to vibrate up and down. Like a mass on a spring, the air oscillates with a particular frequency that depends on the system’s characteristics. We hear this vibration as a a deep hum, but in the high-speed video above, you’re actually seeing the vibration as smoke pulsing in and out of the bottle. Helmholtz resonance shows up more than just in blowing across beer bottles; it’s also a factor in many resonating instruments, like the guitar. To learn more about the physics and mathematics of the effect, check out this page from the University of New South Wales. (Video credit: N. Moore)
February 27, 2015
Singing Toads
Many male frog and toad species sing during warmer months to attract mates. Some, like the American toad in the photo above, can be heard for an impressive distance. Here’s a video of an American toad in action. To sing, these amphibians close their mouth and nostrils, then force air from their lungs past their larynx and into a vocal sac. As with human sound-making, forcing air past the frog’s larynx vibrates its vocal cords and generates noise. That noise resonates in the vocal sac, amplifying the sound and driving the ripples seen in the photo. (Image credit: D. Kaneski; submitted by romannumeralfive)
February 13, 2015