Because we cannot see it, the power of sound is often overlooked; it is an intangible entity, difficult to imagine it as a force in its own right.
Yet, for those of us lucky enough to be able to hear, sound is all around us constantly, having an insidious, often imperceptible, effect on our behavior, moods and reactions. Sound can soothe and calm, enrage and incite, with these emotions being triggered by actual physical responses in the brain caused by various types of noise exposure.
Sound waves can also be utilised as an energy force that can be applied in many different ways: Peter Davey, a 92 year old from Christchurch, New Zealand, has invented a device that uses sonic waves to heat water. When the sonic boiler is immersed in a container of water it can boil it within seconds without losing significant quantities of the liquid as steam.
Medically, sound waves are being used to heal wounds and even kill cancer cells. A technology known as "MIST" has been shown to repair difficult-to-heal wounds such as ulcers in under 12 weeks. The procedure involves spraying a saline solution of the affected area and then apply low-frequency sound waves, and research studies have shown very promising results. Even more exciting uses for sound waves was found in 2012 by researchers at Princess Grace Hospital in London, who have used them to destroy cancer cells. Using High Intensity Focused Ultrasound (HIFU), the team were able to target specific cells, heat them up and kill them, successfully eradicating cancer cells in test subjects suffering from prostate cancer patients.
More recently, a Japanese technology team has made a breakthrough discovery in the area of acoustic levitation. Acoustic levitation is not a new concept, and experiments in the field have been conducted since the early part of the 20th century, where scientists have been able to levitate small objects such as bees, ants and fish using sound waves.
Acoustic levitation uses the air pressure of ultrasound waves (sound with frequencies higher than the range of human hearing) to raise objects, an effect which has been recognized in theory since at least the 1930s. The levitating force has been found to be at its most powerful when the object to be levitated is approximately the same size as the wavelength of the ultrasound waves, and Chinese scientists at Northwestern Polytechnical University in Xian have previously used this method to levitate even heavy balls of tungsten.
Now Japanese researchers, in a study submitted to the Cornell University Library's physics archive and conducted by a team of the University of Tokyo, have taken the process one stage further.
Instead of merely raising test objects, the scientists have been able to move them through space in every direction. The team, which was led by Yoichi Ochiai, was able to demonstrate ultrasonic levitation operating in three dimensions.
During the study, plastic beads were moved in three dimensions with an array of 285 sound-emitting transducers as the controllers, emitting ultrasonic sound waves pitched above the range of human hearing. The array of sound-emitting transducers created a cross-shaped lattice of points in the air where sound waves combined and reinforced one another to create the lifting pressure that levitated the objects.That means the device created a series of points in the air where beads or other objects would seem to just hang in place without any support.
The research marks a new level of control in acoustic levitation. It was the use of more transducers using a basic control system powered by advanced modern computers that enabled the advance to three-dimensional movement, according to acoustic levitation expert Rick Weber of Materials Development Inc. in Arlington Heights, Illinois.
"It is a real advance, and it opens new possibilities for levitation," he said.
Other items, such as beads, electronics parts, matches, screws, nuts, and alcohol droplets were also put through their paces by the University of Tokyo team, who were able to achieve right-left, up-down, and backward-forward motions within their 20.5-inch-wide (520-millimeter-wide) levitation chamber. The movements were controlled by altering the strength of the sound waves emitted by the arrayed speakers in synchronized fashion.
The research is just another amazing illustration of the possible uses of sound waves, and it is probable that their full potential has yet to be realised. Their astounding properties may not be a new discovery, however, as it is possible that the ancients utilised sound for a variety of different functions. A recent theory regarding the iconic stone circle at Stonehenge, in Wiltshire, England, postulated that the bluestone used for the huge monoliths was chosen for expressly for its acoustic properties, and that the ancient monument could actually have been built as a venue where the use of sound was very important.
A study conducted by researchers at the Royal College of Art in London began by tapping on more than 1,000 rocks in the Carn Menyn area of the Preseli Hills in south west Wales, the region where the iconic monument's bluestones are believed to have been sourced.
"We found it was a noteworthy soundscape, with a significant percentage of the actual rocks making metallic sounds like bells, gongs, tin drums, etc., when tapped with small, handheld 'hammerstones,'" study co-leader Paul Devereux, a research associate at the college and an expert in archaeo-acoustics.
The study then moved to the Stonehenge itself, where markings on the stones indicate that they may have been tapped in a similar way, though it is not clear whether this was for acoustic purposes. Nevertheless, when the stones were struck by the researchers they produced "distinctive if muted sounds", and the team believe that the sounds would have resonated more fully had there been sufficient space around them.
"The stones may have been thought to have magical, qualities because of their exceptional sonic nature," Devereux commented, adding that the stones may have been revered for their sound qualities.
There is also a school of thought that suggest the Egyptian Pyramids were raised by sound levitation, a concept that has been circulated by researchers such as Chris Dunn, author of the book The Giza Power Plant: Technologies of Ancient Egypt. As an engineer of some 45 years experience, Dunn was fascinated by the seemingly impossible process that was used to transport the colossal stone blocks when the pyramids were built. He investigated a claim known as the "Coral Castle Mystery" put forward by Edward Leedskalnin, an eccentric Latvian recluse living in Florida. Leedskalnin said that he had constructed a castle from enormous blocks of coral that weighed between 20 to 30 tons each; the castle took him 28 years to complete and he claims to have done it all by himself. Leedskalnin took the secret of its construction with him to his grave, but acoustic levitation, or the use of magnetic energy, has been postulated as one possible theory for his amazing feat.