For some people, a musical tone is enough to induce vertigo and feelings of being drunk. These individuals often have a small hole or defect in the bone that surrounds the canals of the inner ear. Normally, the fluid inside these canals reacts when we rotate our heads, triggering a counterrotation of our eyes that helps stabilize the image on our retinas. But when there’s a defect in the bone surrounding the canal, certain acoustic tones may pump that fluid directly. The patient’s eyes then try to correct for a rotation that’s not occurring, thereby inducing dizziness and vertigo. (Image credit: M. Moiner; research credit: M. Iversen et al.; submitted by Marc A.)
Tag: sound
Hearing in Space
Everyone knows that, in space, no one can hear you scream. Sound is a wave that requires a medium to travel through, and if space is empty, there’s no medium to carry that sound. Except, as Mike from The Point Studios explains, empty is a relative term. Space is full of dust and gas and plasma, just not as full of that matter as we’re used to. Thus, the question of whether sound can travel through space turns into a matter of scale. If the scale–the wavelength–of a sound is much larger than the distance between molecules, then the sound can propagate. So there CAN be sound in space – it just has to have a very long wavelength and, thus, a very low frequency. Check out the video for the full story! (Video credit: The Point Studios)
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)
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)
Sound Interactions
Sound waves often interact with many objects before we hear them. Understanding and controlling those interactions is a major part of acoustic engineering. The animations above show shock waves–sound–from a trumpet interacting with different objects. The sound is made visible using the schlieren optical technique, allowing us to observe the reflection, absorption, and transmission of sound as it hits different surfaces. Fiberboard, for example, is highly reflective, redirecting the sound waves along a new path without a lot of damping. In contrast, the metal grid is only weakly reflective and a small portion of the incoming sound wave is transmitted through the grid. To see more examples, check out the full video, and, if you want to learn more about acoustics, check out Listen To This Noise. (Image credits: C. Echeverria et al., source video)
“Cymatics”
Nigel Stanford’s new “Cymatics” music video is full of stunning science-inspired visuals. The entire video is set up around various science demos–many of which will be familiar to readers–that translate sound or vibration into visual elements. The video uses ferrofluids, vibrates vodka on a speaker to create Faraday waves, and visualizes resonant sound waves with a Rubens’ tube. I don’t want to give away all the awesome effects, so watch it for yourself, and then check out their behind-the-scenes page where they talk about how they created each effect. (Video credit: N. Stanford; submitted by buckitdrop)
Also, today is the final day of voting for the Vizzies, an NSF-sponsored contest for the best science and engineering visuals. Head over to their website to check out the finalists and choose your favorites!
Acoustic Levitation in Three Dimensions
Acoustic sound is a form of pressure wave propagating through air or another fluid. Place a speaker opposite a plate, and its sound will reflect off the surface. The original pressure wave and its reflection form a standing wave. With intense enough sound waves, the acoustic radiation pressure can be large enough to counter the force of gravity on an object, causing it to levitate. We’ve shown you several examples of acoustic levitation before, including squished and vibrating droplets and applications for container-free mixing. Today’s video, however, shows the first acoustic levitation system capable of manipulating objects in three dimensions, an important step in developing the technology for application. (Video credit: Y. Ochiai et al.; via NatGeo)
Sound and Harmonics
The vibrations we perceive as sound, whether in air, water, or any other fluid, are tiny pressure waves emanating from a source, transmitting like ripples across a pond, and finally being caught by our ears and translated by our brains. In this video, the mechanisms and mathematics of sound and harmonics are explained. Although we’re most familiar with these concepts in acoustics, the same principles are used when studying other oscillatory motions, including pendulums, mass-spring systems, disturbances in boundary layers, and the vibrations of a diving board. All of these things rely on the same fundamental principles and mathematics.
The Sound of Helium
Gases of different density are good for more than just physics demonstrations. They also affect the transmission of sound waves, thereby altering our perception of pitch. As fun as sulfur hexafluoride is, though, don’t go playing with it at home; it’s an extremely potent greenhouse gas.
