Tag Archives: sound

Speakers: Sound From Any Surface

Although accustomed to thinking about speakers when we hear of sound reproduction, nature uses several methods of producing sound or amplifying it. For instance, a cricket makes a chirping sound by rubbing its hind legs against each other, while perching on a large leaf to amplify the sound it produces. A guitarist amplifies the sound from the wires by coupling it to the guitar’s wooden box.

Traditionally, the size of the cone and the driver of a speaker determine the frequency and range of sound it produces. That is why several small portable speakers sound tinny, as they are unable to offer the deep bass because their driver can deliver limited frequency ranges. That is also the reason high fidelity audio systems have separate speakers for reproducing extremely low frequencies through subwoofer speakers.

A new type of speaker in the market does not require a cone to reproduce sound. This speaker uses the Incisor Diffusion Technology to diffuse sound across and through any surface upon which it is resting. It uses the surface to act as its cone and the surface diffuses the sound into the surrounding area.

Created by Damson, all its products using the Incisor Diffusion Technology offer a full audio frequency range from the surfaces they are placed upon. However, as different surfaces have varying resonance properties, the audio they produce will sound somewhat different. This unique way of reproducing sound offers the hearing impaired to feel sound through vibrations—just as Beethoven did.

As Damson pushes the capabilities of sound reproduction to newer frontiers, the need for different speakers to provide bass, middle, and high frequencies is fast dissolving. A regular speaker has a coil fixed to a permanent magnet, the arrangement being known as the driver. The Incisor Diffusion Technology from Damson replaces the coil with teeth or incisors. While they act in the same way as a coil does, they also power the different frequencies pushing the through to the surface. The reaction of the Incisor Diffusion Technology with the surface transfers the sound through it. For instance, placing on of Damson speakers on a window diffuses the sound through the glass, allowing it to be heard on both its sides.

Along with the size and shape of the surface, its type also affects the sound that it delivers. For instance, a bigger surface produces more sound than a smaller surface does, as it has more area and moves a greater amount of air—just as a bigger speaker is louder than a smaller one is. Any elastic surface will work to amplify the sound through it.

That means some surfaces work better than others do when reproducing sound. For instance, you will not hear sound from surfaces made of granite or stone, thick solid wood, sand, tarmac, grass, mud, asphalt, and concrete. On the other hand, thin wood is an ideal surface for sound reproduction, as is glass such as windshields, shower screens, windows, and tables. Metals surfaces are also good for sound production, so one can use the car bonnet, hood, or the roof. Now Redux is planning to use this technology on the screen of smartphones as a replacement for tiny speakers.

Why do Speakers use Ferro-fluids?

Speakers reproduce sound by moving a diaphragm to displace air. The mechanism resembles a permanent magnet electric motor. The major difference is the voice coil in a speaker moves linearly instead of in a circular motion. As the coil moves back and forth in step with the electrical signals fed to it, it moves the attached diaphragm. To prevent spurious movements and unwanted oscillations of the diaphragm, conventional speakers generally use a damper. To produce sound from such speakers, extra energy is necessary to overcome the resistance of the damper.

Additionally, the damper has its own natural frequency of vibration that restricts the speaker from reproducing sound accurately at all frequencies. A new technique using a magnetic fluid to replace the damper claims to correct this anomaly by reducing energy consumption and allowing louder and clearer sound across the entire range of frequencies the speaker is capable of reproducing. To quantify the advantages, the new speaker reduces energy consumption by 35% for reproducing the same loudness of sound as from conventional speakers and the improvement in sound quality is nearly 3dB.

NASA originally developed the magnetic fluid in the 1960’s, using it for space exploration and called it Ferro-fluid. It responds to applied magnetic fields because the fluid is infused with Nano-sized magnetic particles. They do not agglomerate or cluster together because of a coating of suitable surfactants. The unique characteristic of ferro-fluids makes them useful in a range of applications. Using applied magnetic fields to control flow or movement, ferro-fluids can replace mechanical parts such as vehicle suspensions, flow of fuel in a reactor and more.

In a conventional speaker, the damper holds several components such as the diaphragm and spring in place, even when the speaker is vibrating. However, the damper causes friction while moving, thereby distorting the original sound waves with secondary vibrations, which are manifest as noise. To overcome the friction requires additional energy while driving and that reduces the speaker’s total volume output by a few decibels.

When replacing the damper in a speaker, the ferro-fluid used has a thickness of only a few microns. The magnets of the speaker create a permanent magnetic field to which the ferro-fluid responds by holding the diaphragm and the coil in place while allowing them to move linearly without any friction. As there are no secondary vibrations from the ferro-fluid, the sound is clearer. The lack of friction allows the speaker to save about 35% of the energy as compared to conventional speakers with dampers.

Ferro-fluids used for the audio field are usually based on two classes of carrier liquids – synthetic enters and hydrocarbons. Both oils are low in volatility and high on thermal stability. The environmental considerations dictate the choice of the fluid used, along with the best balance of viscosity values and magnetization for optimizing the acoustical performance.

Using different carrier liquids and by varying the quantity of magnetic material in the ferro-fluid, it can be tailored to meet different needs. The saturation magnetization depends on the nature of the suspended magnetic material and its volumetric loading. Care is taken to use material whose density and viscosity correspond closely to that of the carrier fluid.