Speaker cone materials can be a deep rabbit hole ranging from inexpensive paper to kevlar. We’ve all cut apart, or blown out, the cheapies to see their inner workings, but the exotic material list does not stop at audiophile-quality models. It can include mirrors, microwave ovens, and a European hacker’s forehead. Video also after the break. In addition to the speakers with expensive elements, there are sound-generating transducers with no cones. These are sometimes called surface speakers, and they vibrate something, anything, to make a sound. At their cores, they have many of the same parts, and making a surface speaker from a traditional speaker is not difficult.
The first step is to find a raw speaker, one with no crossover components, possibly from a garage sale or from a set your spouse insists are outdated, ugly, and better off as firewood. Power specifications should not change since we will be using the same solenoid, and that means your amplifier can follow the speakers back from the dead. The video provides step-by-step instructions, and the goal is to create a module with a moving shaft, but the range must be limited so it cannot be pushed back into the speaker or pulled away, both could destroy it. Once you have that, go around and make everything noisy. Don’t use this on pets or children, but spouses are fair game.
We would love to see a chip bender experiment with different speaker mediums to add an extra layer of complexity, but for the rest of us, bone conduction is already a real thing, and if you enjoy impractical speakers, you are not the only one with your head in the clouds.
In a move guaranteed to send audiophiles recoiling back into their sonically pristine caves, two doctoral students at ETH Zurich have come up with an interesting way to embed information into music. What sounds crazy about this is that they’re hiding data firmly in the audible spectrum from 9.8 kHz to 10 kHz. The question is, does it actually sound crazy? Not to our ears, playback remains surprisingly ok.
You can listen to a clip with and without the data on ETH’s site and see for yourself. As a brief example, here’s twelve seconds of the audio presenting two versions of the same clip. The first riff has no data, and the second riff has the encoded data.
You can probably convince yourself that there’s a difference, but it’s negligible. Even if we use a janky bandpass filter over the 8 kHz -10 kHz range to make the differences stand out, it’s not easy to differentiate what you’re hearing:
Lasers work by emitting light that is “coherent” in that it doesn’t spread out in a disorganized way like light from most sources does. This makes extremely focused beams possible that can do things like measure the distance from the Earth to the Moon. This behavior isn’t just limited to electromagnetic waves, though. [Gigs] via [CodeParade] was able to build a device that produces a tightly focused sound wave, essentially building an audio laser.
Curiously enough, the device does not emit sound in the frequency range of human hearing. It uses a set of ultrasound speakers which emit a “carrier wave” in the ultrasound frequency. However, with a relatively simple circuit a second signal in the audible frequency range is modulated on top of it, much the same way that an AM radio broadcast has a carrier wave with an amplitude modulated signal on top of it. With this device, though, the air itself acts in a nonlinear way and demodulates the signal, producing the modulated signal as audible sounds.
There are some interesting effects of using this device. First, it is extremely directional, so in order to hear sound from the device you would need to be standing directly in front of it. However, once the ultrasound beam hits a solid object, the wave is instantly demodulated and reflected from the object, making it sound like that object is making the sounds and not the device. It’s obvious that this effect is hard to experience via video, but it’s interesting enough that we’d like to have one of our own to try out. It’s not the only time that sound waves and electromagnetic waves have paired up in interesting ways, either.