3D sound systems using groundbreaking piezoelectric springs

November 28, 1999

Digital speakers that can project three dimensional sound across a room are being developed using new springs built from piezoelectric ceramics. Applying an electrical current to the material forces the spring to expand causing a vibration that produces a coherent sound image away from the speaker.

Piezoelectric materials such as quartz are used in digital watches and computers to produce stable vibrations at high frequencies. Polycrystaline ceramics, such as PZT (lead zirconate titanate), can be made to mimic the behaviour of these natural monocrystaline materials by polarising the crystals within the ceramic. This is done by applying an electric field to the material at high temperature to align the microscopically small piezoelectric domains within the material. This produces a net polarisation in the direction of the electric field which, when a smaller electric field is later re-applied to the material, causes a strain in the direction of the polarisation. In traditional speakers, these materials are used in transducers to convert the digital pulse into a vibration that expands and compresses the air to form an audible sound wave.

By using helical springs of the material, items once though to be nothing more than a laboratory novelty, the development team at the University of Birmingham and commercial company 1ŠLimited is breaking new ground. The new transducers developed by the team are constructed from a traditional piezoelectric ceramic coiled like a spring around an inner section containing a bearing and a moveable core. When an electric current is applied, the spring attempts to coil or uncoil, affecting the pressure inside the linear bearing. If the coiling is made greater at one end than the other, the core will be forced to move along the axis of coil in line with the applied voltage. This movement, similar to the movement of a hand squeezing a wet bar of soap, generates a vibration of the air next to it and therefore producing noise. An array of these devices, through a trick of human audio perception, can be used to produce a coherent sound image away from the speaker resulting in a three dimensional sound profile.

Prototypes of the ceramic helices have already been made and work in the way expected, says Dr David Pearce from the University of Birmingham. ³Further work is progressing on assembling the whole device into a working actuator,² says Pearce. ³Working prototypes of these speakers will hopefully be produced in the next couple of years, with marketable products in the years after that.²
This item is due to appear as an article in the December issue of Materials World, the journal of the Institute of Materials.(Due for publication on 1.12.1999)

Notes For Editors 1. Brief contents of Materials World, The journal of The Institute of Materials, are also available on the web: www.materials.org.uk

Institute of Materials

Related Electric Field Articles from Brightsurf:

Charging electric cars up to 90% in 6 minutes
POSTECH Professor Byoungwoo Kang's research team uncovers a new Li-ion battery electrode material that can achieve high-energy density and high power capability per volume without reducing particle size.

uOttawa researchers find cheaper, faster way to measure the electric field of light
Researchers at the University of Ottawa have created a new method to measure the temporal evolution of electric fields with optical frequencies.

How dangerous are burning electric cars?
What happens if an electric car burns in a road tunnel or an underground car park?

One more hit from rare Earth: Efficient coherent spin manipulation by the electric field
Researchers used rare earth ions to efficiently couple the electric and magnetic behaviors of material.

Battery breakthrough gives boost to electric flight and long-range electric cars
Researchers at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), in collaboration with Carnegie Mellon University, have developed a new battery material that could enable long-range electric vehicles that can drive for hundreds of miles on a single charge, and electric planes called eVTOLs for fast, environmentally friendly commutes.

Deterministic reversal of single magnetic vortex circulation by an electric field
Chinese researchers discover a deterministic reversal of magnetic vortex circulation in a Ni79Fe21 (NiFe) island on top of a layered-perovskite Bi2WO6 (BWO) thin film using an electric field.

4D electric circuit network with topology
Researchers from China and Germany have proposed a design scheme to implement a four-dimensional topological insulating state in circuit network, which provides a convenient physical platform for studying high-dimensional states.

How we might recharge an electric car as it drives
Stanford engineers demonstrate a technology that could one day be scaled up to power a car moving down the road.

Electric cars better for climate in 95% of the world
Fears that electric cars could actually increase carbon emissions are unfounded in almost all parts of the world, news research shows.

O-FIB: Far-field-induced near-field breakdown for direct nanowriting in an atmospheric environment
Nanoscale texturing, drilling, cutting and spatial sculpturing require not only high accuracy, but also the capability of manufacturing in the atmospheric environment.

Read More: Electric Field News and Electric Field Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.