Good vibrations no longer needed for speakers as research encourages graphene to talk

May 4, 2017
New research allows sound frequencies to be mixed together, amplified and equalized -- all within the same millimeter-sized device. Credit: David Horsell / University of Exeter

A pioneering new technique that encourages the wonder material graphene to "talk" could revolutionise the global audio and telecommunications industries.

Researchers from the University of Exeter have devised a ground-breaking method to use graphene to generate complex and controllable signals. In essence, it combines speaker, amplifier and graphic equaliser into a chip the size of a thumbnail.

Traditional speakers mechanically vibrate to produce sound, with a moving coil or membrane pushing the air around it back and forth. It is a bulky technology that has hardly changed in more than a century.

This innovative new technique involves no moving parts. A layer of the atomically thin material graphene is rapidly heated and cooled by an alternating electric current, and transfer of this thermal variation to the air causes it to expand and contract, thereby generating .

Though the conversion of heat into sound is not new, the Exeter team are the first to show that this simple process allows sound frequencies to be mixed together, amplified and equalised - all within the same millimetre-sized device. With graphene being almost completely transparent, the ability to produce complex sounds without physical movement could open up a new golden generation of audio-visual technologies, including mobile phone screens that transmit both pictures and sound.

New research allows sound frequencies to be mixed together, amplified and equalized - all within the same millimeter-sized device. Credit: David Horsell / University of Exeter

The research is published in leading journal, Scientific Reports.

Dr David Horsell, a Senior Lecturer in the Quantum Systems and Nanomaterials Group at Exeter and lead author of the paper explained: "Thermoacoustics (conversion of heat into sound) has been overlooked because it is regarded as such an inefficient process that it has no practical applications. We looked instead at the way the sound is actually produced and found that by controlling the electrical current through the graphene we could not only produce sound but could change its volume and specify how each frequency component is amplified. Such amplification and control opens up a range of real-world applications we had not envisaged."

The new applications the team have in mind include ultrasound imaging, for use in hospitals and other medical facilities in the future.

The known high strength and flexibility of would allow intimate surface contact leading to much better imaging. Moreover, the fact that the acoustic devices the Exeter team have devised are simple and cheap make such concepts as intelligent bandages that monitor and treat patients directly a real possibility.

Dr Horsell added: "The frequency mixing is key to new applications. The sound generating mechanism allows us to take two or more different sound sources and multiply them together. This leads to the efficient generation of ultrasound (and infrasound). However, the most exciting thing is that is does this trick of multiplication in a remarkably simple and controllable way. This could have a real impact in the telecommunications industry, which needs to combine signals this way but currently uses rather complex and, therefore, costly methods to do so."

Explore further: Bringing graphene speakers to the mobile market

More information: M. S. Heath et al, Multi-frequency sound production and mixing in graphene, Scientific Reports (2017). DOI: 10.1038/s41598-017-01467-z

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30 comments

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michbaskett
3.7 / 5 (3) May 04, 2017
This might be useful for commo but for it to be useful for music the transfer of heat from membrane to air would have to be phenomenally fast in order to handle the apsects that confer "thereness" to musical reproduction. I remain sceptical.
Telekinetic
May 04, 2017
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Telekinetic
May 04, 2017
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Telekinetic
May 04, 2017
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Telekinetic
May 04, 2017
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Telekinetic
May 04, 2017
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Telekinetic
May 04, 2017
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rrrander
1 / 5 (1) May 05, 2017
Graphene is a flop. Just like carbon nanotubes (Remember the "space elevator?"), buckyballs, quantum dots, etc. People working on this stuff should be conning people out of their money using one of those crowd-funding mechanisms.
Da Schneib
5 / 5 (2) May 05, 2017
If you're gonna make your bass shake a coliseum, you're still gonna need to move some serious air. Which you ain't gonna do with a millimeter square chip.
daqddyo
5 / 5 (1) May 05, 2017
Perhaps this innovation would be feasible for producing nice sound in earbuds.
antialias_physorg
4.2 / 5 (5) May 05, 2017
It's probably useful for ultra-flat integrated sound systems (e.g. directly integrated into your wallpaper). Also any use case where mainenance/replacement would be extremely expensive or downright impossible.

It's the way most all technologies should go eventually: no moving parts.
Telekinetic
not rated yet May 05, 2017


It's the way most all technologies should go eventually: no moving parts.


That is patently absurd. The reason audiophiles invest in high end turntables is the way the MOVING tonearm and cartridge interface with the musical source- the vinyl record, but I'm sure you're pleased with your MP3's. Extolling the virtues of no moving parts is like rallying for impotence.
antialias_physorg
5 / 5 (4) May 07, 2017
The vast majority of people can't tell the difference between mp3 and analog audio. If you can: good for you. Play with your antiques and be happy.
For the rest: give them what is - to their ears- the best quality they can discern and do it in a way that doesn't require maintenance or expensive equipment. There's absolutely no point in going beyond that.

To each their own. I don't recommend that everyone buy a high end desktop and graphics card as a coding platform, either. Most people are served perfectly fine by a tablet or low end laptop for their computing needs.
rrrander
not rated yet May 07, 2017
It's probably useful for ultra-flat integrated sound systems (e.g. directly integrated into your wallpaper). Also any use case where mainenance/replacement would be extremely expensive or downright impossible.

It's the way most all technologies should go eventually: no moving parts.


To move air, you need movement. No air movement, no sound.
Whydening Gyre
5 / 5 (1) May 08, 2017
If you're gonna make your bass shake a coliseum, you're still gonna need to move some serious air. Which you ain't gonna do with a millimeter square chip.

"Serious Air" would be a great name for an amplifier company...:-)
But - Absolutely the ONLY way to convey acoustics and their nuancery, cuz that's what sound IS...:-)
antialias_physorg
5 / 5 (2) May 08, 2017
To move air, you need movement. No air movement, no sound.

The idea here is to heat air. Heated air expands. If you do this fast and often enough per second you can create vibrations which are in the audible range. None of the hardware of the system moves.

If you're gonna make your bass shake a coliseum, you're still gonna need to move some serious air. Which you ain't gonna do with a millimeter square chip.

Well, you might get it by focussing some multi-megawatt microwave rigs on an air volume. Not that this would be particularly efficient (or safe), but I think scientists could come up with half a dozen ways of getting serious bass going without any moving parts.
Da Schneib
5 / 5 (1) May 08, 2017
@antialias, I expect these things will be good for headphones and stuff like that. In fact I expect they'll be pretty kickass for that sort of thing. But they're not gonna replace real speakers for live performance, at least not for bass. Also, I happen to be one of those who can detect the difference between lossy and lossless compression. Nothing inherently wrong with MP3, as long as the compression isn't lossy.

@Whyde, heh, specializing in D-class power amps with tube preamps, no doubt. You play?
Da Schneib
5 / 5 (1) May 08, 2017
BTW, @antialias, there's a reason that guitar players like tube amps, and it has to do with the type of distortion overdriven 12AX7s give. One can control the sound by one's dynamics, both right and left hand, when one gets it set just right. And it never gets so edgy no one will listen to it; transistors just don't give the same harmonics as tubes. But that's in the small-signal domain; for large signal, transistors do just fine. See Linn Amp.

I've never understood why so-called audiophiles think tube amps are good for general musical reproduction; the entire idea is to get the right kind of distortion for your instrument, and a real audiophile doesn't want any distortion in the reproduction, only in the production. I use tubes for my guitar amps, and transistors and the digital domain (lossless, mind you) for my home theater. Each has its place. But lossy compression is bad audio. I got none of that, thanks.
antialias_physorg
5 / 5 (2) May 08, 2017
But they're not gonna replace real speakers for live performance

Probably not. Unless we move to directed audio where the signal is directed precisely to the ear of the listener (and audible nowhere else). Arrays of these devices would be ideal for that.
In that case it doesn't matter if the entire stadium is filled with sound waves or whether you get the sound 'beamed' to you. (Ok, close to the speakers you may lack the bodily effect of high amplitude soundwaves. But further away it would actually improve the quality of the experience, as you don't get multiple echos and all the incidental noise)

as long as the compression isn't lossy.

Mp3 is lossy (in a way). It's a psychoacoustic packing algorithm that cuts out large decibel differences (since the ear/mind cannot process a quiet sound while a loud sound is playing. The quiet sound isn't encoded.) Someone with a hearing deficit in the frequency of the loud sound can notice.
Da Schneib
5 / 5 (1) May 08, 2017
Hmmmm, my experience is that it's the quiet sounds during loud passages that really test a rig. A good rig can reproduce both simultaneously, and this is one of the measures of a really hot rig.

If you've never heard "Etude" by Lee Ritenour, I suggest you listen to it. I test rigs with it. If I can't hear the fingering on the bass I know I'm listening to an inferior rig. Muddy bass is a major defect, and lots of people don't know to check for it.
Da Schneib
5 / 5 (1) May 08, 2017
Let me give you a fairly modern example: "Since I Been Lovin' You," Led Zeppelin 3. You can hear the squeaks of Bonham's bass pedal and the fingering on Jones' bass while Jimmy is wailin'. This gives the recording "bottom" that puts you in the studio, and if it's missing, believe me I'll hear it. And unfortunately, I have.
antialias_physorg
5 / 5 (2) May 08, 2017
You can hear the squeaks of Bonham's bass pedal and the fingering on Jones' bass while Jimmy is wailin'.

Though one could debate whether this is part of the music ;)

Just kidding. If those nuances are important then that's fine. I would wager, though, that the overwhelming part of listeners aren't listening (or appreciating) this music because of these noises.

It's like we keep telling our coders (and what I have to keep telling myself whenever I write code at home): Don't make golden faucets. They look pretty, but at the end of the day it's the effect you want to create with your code that counts.
Da Schneib
5 / 5 (1) May 08, 2017
That's just an example. And, I have to admit, not all that good a one, but it's what came to mind. The question is, do you hear everything they recorded, or not?
antialias_physorg
5 / 5 (2) May 08, 2017
To me the question would be: Does the recording produce the desired effect?
a) If you're aiming to capture a most truthful recording of what actually happened ('raw data') then every nuance counts.
b) If you're trying to get music accross to a listener for maxium enjoyment (i.e. a level at which increased quality does not increase enjoyment) at a minimum of bandwith then that's where mp3 is (near) optimal.

a) would be what I'd use in a scientific context (i.e. for 'purists' approach. People who want to do actual measurements on the data)
b) is what I'd endorse for the casual user as there's no benefit beyond that

It's like with anything else (writing articles, structuring an argument, ... ) : Is the article/argument important? Or is the effect on the reader important?
Da Schneib
5 / 5 (1) May 08, 2017
It's a matter of taste, and I can hear when there's stuff happening that's just not being caught by the recording medium, and it irritates me. Listening to music, for me, is an activity, like reading a book. Or eating a meal. It's not just background noise. I note not only the song, but the production quality- I can't help it, I know what goes into it having done some recording myself.
Whydening Gyre
not rated yet May 08, 2017
... Nothing inherently wrong with MP3, as long as the compression isn't lossy.

Lossless Bass is essential.
@Whyde, heh, specializing in D-class power amps with tube preamps, no doubt.

If you're talking about the ones that crack your windows when you play - yes...:-)
You play?

Not to any depth for a long time. (Hand injury in Army) My guitar sits on on the stand in the corner of my study. I hear a song and think - "Hey, I could play that..." and then try.
Miserably, of course...:-)

Telekinetic
5 / 5 (1) May 08, 2017
The greatest experience of music is a "live" performance- whether it's Carnegie Hall, rock concert, or jazz club- it's there that you'll find sonic qualities superior to any audio reproduction. That doesn't mean one should stop trying to get close to that ideal. As a civilization. we should reach for the highest level of sound reproduction and shun mediocrity. technological dumbing down, and condescension to those who "can't tell the difference." Historically, the great conductors of orchestras sweated bullets to bring music to near perfection, so why listen to it with a crappy system or format. Music pierces directly into the soul, so the electronic vehicle had better be able to deliver it.
Da Schneib
5 / 5 (1) May 08, 2017
Nothing worse than muddy bass.

With a D-class power amp, you get high efficiency, which means you can pack in a lot of power in a small space without it overheating. The trick would be to separate the tube preamps so their heat doesn't affect the power amp. Nobody's making D-class instrument power amps, though; the math is too tricky for them. It's easier to make a Linn Amp and move on. You'll find more and more D-class power amps in high-end audio setups, though. The big advantage is weight, and power dissipation.

I've been playing thirty years now. Shame about your hand, but keep playin'. It's good for your soul. I quit working on cars when I realized not only my living, but my greatest joy, depend on whole hands.
Da Schneib
5 / 5 (1) May 08, 2017
I just read the Wikipedia article on Class D amps and what a bunch of crap. A Class D power amplifier operates in switched mode, rather than analog mode; the difference between this and a linear-mode amplifier is pretty much the same as the difference between a linear power supply and a switched-mode power supply. Instead of bulky transformers and A- or B-Class lossy transistors that dissipate as much power as they send to the load, switched-mode equipment uses either caps or coils with FETs and high-tech diodes in the switch, and takes input and output through caps or coils as well.

I'm a big fan of Cuk converters, having used them with excellent results on my astronomy rig; they're incredibly efficient, and this is a big deal when you have to lug expensive and heavy batteries around. I find I can get away with a single AGM battery all night with a Cuk converter to condition the power.
[contd]
Da Schneib
5 / 5 (1) May 08, 2017
[contd]
The Cuk converter is the optimum topology; it uses coils at the input and output, and a capacitor in the switch. You spend most of the money on the diode and FET in the switch, and most of the design time on the switch controller. Its single drawback is that ground at the input is not ground at the output, and a lot of EEs freak out about that. It's the price you pay for efficiency. You'll find a lot of Cuk converters on satellites.

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