Stretchable, Flexible, Transparent Nanotube Speakers

An anonymous reader writes "Chinese researchers have realised that a sheet of nanotubes behaves like a speaker when you send an audio current through it. The technology opens the way for a range of new versatile speaker systems. A video shows the speakers in action — some are stretched, one has even been sewn into a flag."

Comments

Audio wallpaper?

[wcrowe]

I wonder how long before this technology is affordable?

Re:Audio wallpaper?

[TheRealMindChild]

Not when you account for how many Monster cables you'd need

Sound Quality/Better speakers

[phantomfive]

This is awesome! The problem with conventional speakers is the have huge difficulty dealing with subtle differences in volume. This means the tone color of recorded sound is never as interesting as real sound. It also gives problems when recording orchestras that get loud and soft. Check Beethoven's ninth symphony for an example, it starts of as soft, like a single instrument tuning, the grows into a deafening roar, whereas the contrast is not nearly as emotional and exciting on a speaker, meaning we miss out if we can't afford our own pocket-orchestra.

In addition, if you click on that link, you will hear violins. However, those violins will not sound like real violins. There is a whole spectrum of musical interest that must be flattened out to get this in a speaker.

Now, however, carbon nanotubes might be the key to unlocking giant sound in your living room. Exciting times!

Wow, I haven't been this excited about new technology since I saw a lazerdisk. And that was just because it was big and shiny.

Re:Sound Quality/Better speakers

[pz]

Sigh. It's great that you're excited and all, but just because there's a new technology for turning electrical input into mechanical work doesn't mean it is an advance in speakers. For example, piezoelectrics were touted as the be-all-end-all for speaker design when they came out. But, it turns out, they are rather bad at being designed into speakers, and even then, they aren't that accurate (although there are certainly exceptions).

The fundamental problem in speaker design is the inescapable mismatch of mechanical impedance between the relatively solid (ie, low mechanical impedance) speaker and the relatively non-solid (ie, high mechanical impedance) air. Using horn loading helps this a lot (the best speakers I've ever hear were horn loaded) as this serves as a mechanical transformer between the speaker and the room air. But what helps more than anything else for a given amount of engineering effort and cost is doing all of the bandpass filtering well before the final amplification stage and having exactly one acoustic driver per amplifier output stage. (If you don't already understand the reasons for this, just ask, I'd love to tell you about them!)

Now, will a curtain of this nanotube stuff work as a speaker? Sounds probable. Will it work well? I doubt it, since to accurately reproduce sound, the actuating mechanism (ie, the cone in a conventional speaker) needs to be as rigid as possible so that the acoustic wave it produces accurately corresponds to the electrical signal delivered to it. Internal distortions in the actuating surface (waves on the cone of a conventional speaker, or on the surface of this nanotube stuff) distorts the output. The larger the actuating surface, the more important its rigidity (read: it needs an extremely low internal mechanical impedance).

The ideal sound source for reproduction is a physical point, not a sheet. The reason speakers have physical extent, rather than being points, is the coupling issue touched upon above: they need to have extent that is comparable to the wavelength they are trying to reproduce in order to have sufficient coupling to the atmosphere -- unless an acoustic coupling mechanism is used, like a horn.

Re:Sound Quality/Better speakers

[4D6963]

Huh... aren't you basically just complaining about a lack of dynamic range which you can blame on the fact that you don't actually play CDs at 110 dB as in concerts? Excuse my ignorance, I'm not an audiophile, just a software engineer specialised in sound processing.

Re:Sound Quality/Better speakers

[phantomfive]

That was an extremely interesting post, but these carbon-nanotube speakers are not vibrating at all! Read the article, they put a laser vibrometer on the thing, and didn't detect a single movement. Now, you have to admit that's pretty great. They think it is happening because of rapid oscillation of temperature, which is what happens with a thermophone. Which is an obscure little thing I had never heard of. They unfortunately don't mention anything about sound quality, but it at least matches youtube's! The idea of carbon nano-tube speakers is something I had not considered, but is definitely cool. I was actually, believe it or not, daydreaming about better headphone speakers last night. Not that I actually have any clue how to do it.

Re:Sound Quality/Better speakers

[ceoyoyo]

While it doesn't necessarily mean it will make a good speaker (the sound on the video sounded pretty bad, but that could be because of the music chosen, the recording, or the video player), but according to the article the mechanism of sound production is not mechanical. Most of your points are quite true when you're actually vibrating a solid to produce the sound, but don't apply otherwise.

Re:Sound Quality/Better speakers

[blincoln]

There is a whole community of people, who tend to listen to classical music, that is EXTREMELY interested in precise musical reproduction. They know what an orchestra sounds like, and they know a CD doesn't reproduce it very well. They will get annoyed if the sound is bumped up just to sound louder.

The problem with most of that type of person is that they refuse to participate in and/or accept the results of double-blind tests to see if they are perceiving something that's actually different or it's a psychological effect.

Anyway, the main issue I'm aware of in terms of dynamic range isn't related to speakers or microphones. It's that all of the standard digital audio systems I'm aware of use linear instead of logarithmic encoding. Digital cameras are the same way. Our ears are logarithmically sensitive, and the exposure model retained from film cameras is too.

For whatever reason (simplicity, I assume?) digital audio and imaging systems use a linear model. This means that in the case of digital audio, half of the bits in each sample are allocated to the top decibel of loudness, just like half of the bits in each pixel of an RGB image are allocated to the top f-stop of brightness. So either the recording is compressed to make the most use of those bits, or a ton of fidelity is thrown away.

If you'd like to experiment with the results of this type of encoding, you can easily simulate an exaggerated version by opening a digital audio file in Audacity (or some other app), reducing its volume to 0.1% (or 0.01%, etc.) and then normalizing it. The sample quantization (and associated added noise) that results is the same thing.

I've heard of experimental systems based on logarithmic encoding, and I'm really not sure why they haven't caught on. The difference in processing difficulty must be negligible with today's technology.

Singing or speaking jackets?

[lumpenprole]

As if ringtones weren't annoying enough. Welcome to hell.

Re:Singing or speaking jackets?

[pushing-robot]

There goes a man with his own theme music.

Re:Singing or speaking jackets?

[pavon]

And I thought my coworker wore loud shirts now.

Waterproof, durable, flexible...

[MadCow42]

To me it seems a natural fit to help "ruggedize" consumer electronics. One of the hardest things to seal on your phone is the speaker (and mic... which this probably wouldn't address in itself).

No more need for a speaker - just put the candybar up to your ear.

OT: Fixing /. displays?

[Maury Markowitz]

No matter what I try, certain articles are collapsed in the main-page view - including this one in Technology. Can someone tell me how to ensure that ALL articles are expanded?

Re:Who remembers...

[boarder8925]

Who remembers the self-drying, speaking jacket in Back to the future II?

Come on, this is Slashdot, man. The right question is, who doesn't?

Re:Rick Roll of Wallpaper

[glittalogik]

Ooooh never gonna zip you up
Never gonna tie you down
Never gonna twist you round and half-Windsor you
Never gonna make you crease
Never gonna say drip-dry
Never gonna catch in your fly and hurt you!