The Most Famous Room In Rock-n-Roll You’ve Never Seen

The study of audio technology has a lot of fascinating branches, and one or two of them even take the curious engineer not into electronics but into architecture. There’s the anechoic chamber with its complete lack of echo, but at the other end of the scale, there’s the echo chamber.

It’s normal in 2024 when searching for reverb to reach for a software plugin, but following the effect back through silicon, spring lines, and metal plates to the 1950s, we find an echo chamber as a real room with a speaker and a microphone placed in it. [Rick Beato] takes us into the echo chamber, starting with one of the few remaining originals and probably the one whose effect has been heard on the most highly-charting music, at the famous Abbey Road studio in London.

The video below the break is broadly in two parts, with the first concentrating on the Abbey Road chamber and the second showing how an empty room in a house can be used to make your own. It’s aimed at musicians rather than hardware hackers but we think it’s one of those moments of crossover that readers might find interesting. We were particularly curious about the tall ceramic tubes in the Abbey Road chamber, designed to further break up the sound waves for a greater depth of reverb.

The video shows how reverb can be achieved with just a room, but don’t worry if you’re space limited. A plate reverb needn’t break the bank. Or, grab a spring.

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Absorbing Traffic Noise With Bricks Using Helmholtz Resonators

One inevitable aspect of cities and urban life in general is that it is noisy, with traffic being one of the main sources of noise pollution. Finding a way to attenuate especially the low-frequency noise of road traffic was the subject of [Joe Krcma]’s Masters Thesis, the results of which he gave a talk on at the Portland Maker Meetup Club after graduating from University College London. The chosen solution in his thesis are Helmholtz resonators, which are a kind of acoustic spring. Using a carefully selected opening into the cavity, frequencies can be filtered out, and extinguished inside the cavity.

Basic functionality and formula used to determine the dimensions of a Helmholtz Resonator.
Basic functionality and formula used to determine the dimensions of a Helmholtz Resonator.

As examples of existing uses of Helmholtz resonators in London, he points at the Queen Elizabeth Hall music venue, as well as the newly opened Queen Elizabeth Line and Paddington Station. For indoor applications there are a number of commercial offerings, but could this be applied to outdoor ceramics as well, to render urban environments into something approaching an oasis of peace and quiet?

For the research, [Joe]’s group developed a number of Helmholtz resonator designs and manufacturing methods, with [Joe] focusing on clay fired versions. For manufacturing, 3D printing of the clay was attempted, which didn’t work out too well. This was followed by slip casting, which allowed for the casting of regular rectangular bricks.

But after issues with making casting hollow bricks work, as well as the cracking of the bricks during firing in the kiln, the work of another student in the group inspired [Joe] to try a different approach. The result was a very uniquely shaped ‘brick’ that, when assembled into a wall, forms three Helmholtz resonators: inside it, as well as two within the space with other bricks. During trials, the bricks showed similar sound-deadening performance as  foam and wood. He also made the shape available on Thingiverse, if you want to try printing or casting it yourself.

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DIY Hydrophone Listens In On The Deep For Cheap

The microphone is a pretty ubiquitous piece of technology that we’re all familiar with, but what if you’re not looking to record audio in the air, and instead want to listen in on what’s happening underwater? That’s a job for a hydrophone! Unfortunately, hydrophones aren’t exactly the kind of thing you’re likely to find at the big-box electronics store. Luckily for us, [Jules Ryckebusch] picked up a few tricks in his 20-year career as a Navy submariner, and has documented his process for building a sensitive hydrophone without needing a military budget.

Fascinated by all the incredible sounds he used to hear hanging around the Sonar Shack, [Jules] pored over documents related to hydrophone design from the Navy and the National Oceanic and Atmospheric Administration (NOAA) until he distilled it all down to a surprisingly straightforward build. The key to the whole build is a commercially available cylindrical piezoelectric transducer designed for underwater communication that, incredibly, costs less than $20 USD a pop.

The transducer is connected to an op-amp board of his own design, which has been adapted from his previous work with condenser microphones. [Jules] designed the 29 x 26 mm board to fit neatly within the diameter of the transducer itself. The entire mic and preamp assembly can be cast inside a cylinder of resin. Specifically, he’s found an affordable two-part resin from Smooth-On that has nearly the same specific gravity as seawater. This allows him to encapsulate all the electronics in a way that’s both impervious to water and almost acoustically transparent. A couple of 3D-printed molds later, the hydrophone was ready to cast.

Interestingly, this isn’t the first homebrew hydrophone we’ve seen. But compared to that earlier entry, which basically just waterproofed a standard microphone pickup, we think this more thoughtful approach is likely to have far better performance.

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James West Began 40 Years At Bell Labs With World-Changing Microphone Tech

I’d be surprised if you weren’t sitting within fifty feet of one of James Edward Maceo West’s most well-known inventions — the electret microphone. Although MEMS microphones have seen a dramatic rise as smartphone technology progresses, electret microphones still sit atop the throne of low-cost and high-performance when it comes to capturing audio. What’s surprising about this world-changing invention is that the collaboration with co-inventor Gerhard Sessler began while James West was still at university, with the final version of the electret springing to life at Bell Labs just four years after his graduation.

A Hacker’s Upbringing

James’ approach to learning sounds very familiar: “If I had a screwdriver and a pair of pliers, anything that could be opened was in danger. I had this need to know what was inside.” He mentions a compulsive need to understand how things work, and an inability to move on until he has unlocked that knowledge. Born in 1931, an early brush with mains voltage started him on his journey.

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Hackaday Podcast 080: Trucks On A Wire, Seeing Sounds, Flightless Drone, And TEA Laser Strike

Hackaday editors Elliot Williams and Mike Szczys flip through the index of great hacks. This week we learn of a co-existence attack on WiFi and Bluetooth radios called Spectra. The craftsmanship in a pneumatic drone is so awesome we don’t care that it doesn’t fly. Building a powerful TEA laser is partly a lesson in capacitor design. And join us in geeking out at the prospect of big rigs getting their juice from miles of overhead wires.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)

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Building DIY Acoustic Panels To Cut Down On Echoes

Plenty of hackers and makers are passionate about content creation. In the dog-eat-ice-bucket-challenge world of online video, production value is everything. If you want to improve your audio quality then cutting down on echoes is a must, and these acoustic panels will help you to do just that. 

The build starts with aluminium L-channel, affixed together into an equilateral triangle with the help of some 3D printed brackets. Two of the triangular frames are then fitted together via a series of hexagonal standoffs. Foam or housing insulation is then added to act as the primary sound absorbing material. To give an attractive finish, the panels are covered in fabric. The panels are then placed on to drywall using nails glued into the standoffs.

While the panels are likely more expensive to build than off-the-shelf foam alternatives, they have an attractive look which is key in video studio environments. If you’re wondering where to position them for the best results, there’s a simple and easy approach to figure it out. Video after the break.

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Build Your Own Anechoic Chamber

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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