sound

85 Articles

Tiny Amplifier With ATtiny

February 12, 2019 by 31 Comments

Small microcontrollers can pack quite a punch. With the right code optimizations and proper use of the available limited memory, even small microcontrollers can do things they were never intended to. Even within the realm of intended use, however, there are still lots of impressive uses for these tiny cheap processors like [Lukasz]’s audio amplifier which uses one of the smallest ATtiny packages around in the video embedded below.

Since the ATtiny is small, the amplifier is only capable of 8-bit resolution but thanks to internal clock settings and the fast PWM mode he can get a sampling rate of 37.5 kHz. Most commercial amplifiers shoot for 42 kHz or higher, so this is actually quite close for the limited hardware. The fact that it is a class D amplifier also helps, since it relies on switching and filtering to achieve amplification. This allows the amplifier to have a greater efficiency than an analog amplifier, with less need for heat sinks or oversized components.

All of the code that [Lukasz] used is available on the project site if you’ve ever been curious about switching amplifiers. He built this more as a curiosity in order to see what kind of quality he could get out of such a small microcontroller. It sounds pretty good to us too! If you’re more into analog amplifiers, though, we have you covered there as well.

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Those Voices In Your Head Might Be Lasers

February 1, 2019 by 21 Comments

What if I told you that you can get rid of your headphones and still listen to music privately, just by shooting lasers at your ears?

The trick here is something called the photoacoustic effect. When certain materials absorb light — or any electromagnetic radiation — that is either pulsed or modulated in intensity, the material will give off a sound. Sometimes not much of a sound, but a sound. This effect is useful for spectroscopy, biomedical imaging, and the study of photosynthesis. MIT researchers are using this effect to beam sound directly into people’s ears. It could lead to devices that deliver an audio message to specific people with no hardware on the receiving end. But for now, ditching those AirPods for LaserPods remains science fiction.

There are a few mechanisms that explain the photoacoustic effect, but the simple explanation is the energy causes localized heating and cooling, the material microscopically expands and contracts, and that causes pressure changes in the sample and the surrounding air. Saying pressure waves in air is just a fancy way of explaining sound.

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Listening To Mains Power, Part 2

January 14, 2019 by 26 Comments

The electricity on the power grid wherever you live in the world will now universally come to you as AC. That is to say that it will oscillate between positive and negative polarity many times every second. The frequency of 50 or 60Hz just happens to be within the frequency range for human hearing. There’s a lot more than this fundamental frequency in the spectrum on the power lines though, and to hear those additional frequencies better you’ll have to do a little bit of signal processing.

We first featured this build back when it was still in its prototyping phase, but since then it’s been completed and used successfully to find a number of anomalies on the local power grid. It takes inputs from the line, isolates them, and feeds them into MATLAB via a sound card where they can be analyzed for frequency content. It’s been completed, including a case, and there are now waterfall diagrams of “mystery” switching harmonics found with the device, plus plots of waveform variation over time. There’s also a video below that has these harmonics converted to audio so you can hear the electricity.

Since we featured it last, [David] also took some feedback from the comments on the first article and improved isolation distances on his PCB, as well as making further PCB enhancements before making the final version. If you’ve ever been curious as to what you might find on the power lines, be sure to take a look at the updates on the project’s page.

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Build Your Own Anechoic Chamber

December 14, 2018 by 16 Comments

For professional-level sound recording, you’ll need professional-level equipment. Microphones and mixing gear are the obvious necessities, as well as a good computer with the right software on it. But once you have those things covered, you’ll also need a place to record. Without a good acoustic space, you’ll have all kinds of reflections and artefacts in your sound recordings, and if you can’t rent a studio you can always build your anechoic chamber.

While it is possible to carpet the walls of a room or randomly glue egg crate foam to your walls, [Tech Ingredients] tests some homemade panels of various shapes, sizes, and materials against commercially available solutions. To do this he uses a special enclosed speaker pointed at the material, and a microphone to measure the sound reflections. The tests show promising results for the homemade acoustic-absorbing panels, at a fraction of the cost of ready-made panels.

From there, we are shown how to make and assemble these panels in order to get the best performance from them. When dealing with acoustics, even the glue used to hold everything together can change the properties of the materials. We also see a few other cost saving methods in construction that can help when building the panels themselves as well. And, while this build focuses on acoustic anechoic chambers, don’t forget that there are anechoic chambers for electromagnetic radiation that use the same principles as well.

Thanks to [jafinch78] for the tip!

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My Oscilloscope Uses Fire

December 12, 2018 by 16 Comments

If you want to visualize sound waves, you reach for your oscilloscope, right? That wasn’t an option in 1905 so physicist [Heinrich Rubens] came up with another way involving flames. [Luke Guigliano] and [Will Peterson] built one of these tubes — known as a Rubens’ tube — and will show you how you can, too. You can see a video of their results, below. Just in case a flame oscilloscope isn’t enough to attract your interest, they are driving the thing with a theremin for extra nerd points.

The guys show a short flame run and one with tall flames. The results are surprising, especially with the short flames. Of course, the time base is the length of the tube, so that limits your measurements. The tube has many gas jets along the length and with a sound source, the height of the flames correspond to the air pressure from the sound inside the tube.

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Superdeep Borehole Samples Create Non-boring Music

October 19, 2018 by 14 Comments

In the 1970s, the Soviet Union decided to dig a hole for science. Not just any hole, the Kola Superdeep Borehole reached a depth of over 12 kilometers, the deepest at the time and the second deepest today by just a few meters. Since this was one of the few holes dug this deep that wasn’t being drilled for oil, the project was eventually abandoned. [Dmitry] was able to find some core samples from the project though, and he headed up to the ruins of the scientific site with his latest project which produces musical sounds from the core samples.

The musical instrument uses punched tape, found at the borehole site, as a sort of “seed” for generating the sounds. Around the outside of the device are five miniature drilling rigs, each holding a piece of a core sample from the hole. The instrument uses the punched tape in order to control the drilling rigs, and the sound that is created is processed by the instrument and amplified, which creates some interesting and rather spooky sounds. The whole thing is controlled by an Arduino Mega.

Not only does the project make interesting sounds from a historically and scientifically significant research station and its findings, but the project has a unique and clean design that really fits its environment at the abandoned facility. The other interesting thing about this project is that, if you want to make the trek, anyone can go explore the building and see the hole for themselves. If you’re wondering about the tools that could be used to make a hole like this, take a look at this boring project.

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Modular Violin Takes A Bow

October 16, 2018 by 10 Comments

They say the only difference between a violin and a fiddle is the way you play it. If that’s so, this modular violin will need a new name, since it can be broken apart and changed in ways that make it sound completely different, all within a few minutes.

The fiddle is the work of [David Perry] and has 3D printed body, neck, pegbox, and bridge. While it might seem useful on the surface as a way to get less expensive instruments out in the world where virtually anyone has access to them, the real interesting qualities are shown when [David] starts playing all of the different versions he’s created. The sound changes in noticeable ways depending on the style of print, type of plastic used, and many other qualities.

Of course you will need a bow, strings, pegs, and a fingerboard, but the rest is all available if you have a 3D printer around. If you’re already a skilled violinist this could be a very affordable way to experiment with new sounds. It’s not the first time we’ve seen 3D printed violins, but it is the first time we’ve seen them designed specifically to alter the way they sound rather than their physical characteristics. If you want to make your own, all of the .stl files are available on the project’s site.

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