Mary Theresa McLean/Pixabay
Sound waves illustration

Graphene Membrane Could Revolutionize Speakers

March 23, 2020
Small speakers with high fidelity could soon be found in headphones, earbuds and cell phones.

Scientists at the Department of Energy’s Lawrence Berkeley National Laboratory have helped advance research into graphene and other ultrathin materials, both in terms of using specialized tools and techniques to make them, and to study their structure and properties at the nanoscale and atomic scale. Some of these research findings are now being used by GraphAudio to make speaker-related components.

The technology licensed from Berkeley Lab in 2016 could be used in a variety of devices, including speakers, earbuds and headphones, microphones, autonomous vehicle sensors, and ultrasonic and echolocation systems.

The speaker developed by the company uses a small, several-layers-thick graphene film or membrane that converts electric signals into sound. The membrane measures about a centimeter across and is stretched on a circular frame. The membrane and supporting frame are sandwiched between silicon-based electrodes driven with alternating voltages.

The electric fields make the membrane and that creates sound in an efficient, controlled way. This design, known as an electrostatic transducer, requires fewer parts and far less energy than more conventional designs, which often require electrical coils and magnets.

In some popular in-ear headphones, only about 10% of the electrical energy gets converted to sound while the rest is lost as heat. The graphene transducer, by contrast, converts about 99% of the energy into sound. The graphene speaker is also almost distortion-free and has an extremely “flat” response across a broad spectrum of sound frequencies, even beyond what humans can hear. This means the sound is of equal quality across a wide range of high and low frequencies, from subsonic all the way to ultrasonic.

Because of the large bandwidth, the graphene transducer could be used for such applications as echolocation systems for submarine communications, ultrasonic sensors for locating survivors in rubble-strewn environments and for high-quality imaging of human fetuses in the womb.

The same properties that make the graphene work well in speakers can also make for high-quality microphones. GraphAudio CEO Ramesh Ramchandani said the company’s sample headphones and microphones demoed at the Consumer Electronics Show in January led to some good discussions with prospective partners. A commercially licensed technology developed by Berkeley Lab and UC Berkeley researchers could be available to consumers within the next couple of years.

The company claims the sound quality of its technology is so crystal-clear, it’s possible to pick out an individual instrument from a symphony orchestra.

Ramchandani noted that flat-screen television technology has all but replaced bulkier and heavier cathode-ray tube televisions; he expects the same sort of transformation in audio products.

Among the products that could emerge from GraphAudio’s licensed technology are thin car speakers embedded in a vehicle’s interior ceiling for better surround sound, and car sensors that rely on two-way echolocation to avoid vehicle collisions.

Berkeley researchers plan on exploring how to make mechanical transducers with ultrathin materials manufactured with tunable elastic properties by putting precisely patterned nanoscale holes or slots in them.

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