A Digital Pitch Pipe Gets You In Tune
By Lewin Day
Some humans are blessed with perfect pitch, an ability that comes in handy when pursuing the musical arts. For many others though, a little help is often appreciated. A pitch pipe is a handy way to find the starting note of a performance, and [Isaac] decided to build his own in the digital realm.
The project is based on the Adafruit Circuit Playground express, which packs in all the peripherals needed right on board. The buttons are used to select the pitch required, with the LEDs used to display the selected note. Blue means flat, green means natural, and red means sharp. A 3D printed outer ring is clipped on to the board to denote the pitches for the user. To play the note, the user simply blows on the pitch pipe. The onboard MEMS microphone detects this and plays the note on the onboard speaker.
It’s a tidy little project that is a great way to get one’s feet wet with embedded programming and working with audio. We’ve seen the Circuit Express pop up before too, such as in this pizza-box DJ mixer. Video after the break.
Impractical Switches for the Bored Maker
By Inderpreet Singh
Cabin fever: the inability to socialize with other humans does weird things to the human brain. Then again some of us are born to stand out, and one such amazing maker, [Lee], is spending time making weird switches from basically anything.
These experiments prove that there is a lot you can do with the stuff you have around your house and the other end of the circuit doesn’t necessarily need to be a humble LED. You could get more interesting results with adding the likes of a microcontroller like an ATtiny. Coupling it with a DIY LED badge would be a great idea and we’d love to see what you come up with.
Stay Smarter Than Your Smart Speaker
By Kristina Panos
Smart speakers have always posed a risk to privacy and security — that’s just the price we pay for getting instant answers to life’s urgent and not-so-urgent questions the moment they arise. But it seems that many owners of the 76 million or so smart speakers on the active install list have yet to wake up to the reality that this particular trick of technology requires a microphone that’s always listening. Always. Listening.
So what are the best practices of confidential work in earshot of these audio-triggered gadgets?
Hey Alexa, Who’s to Blame?
On the one hand, people and their tastes are the problem. That sleek cylinder or stubby hockey puck of an assistant is designed to be attractive enough that people will display it prominently in their homes. Most people don’t want their appliances to come with constant reminders of their inherent dangers, because warnings are visual noise.
Take stoves for instance. Stoves designers assume that their users have a certain level of base knowledge. It goes with out saying that hot stoves are hot, but you weren’t born knowing that — you either learn that by burning your hand, or by heeding the warnings of other humans.
With smart speakers, the downsides are far less obvious, and the injury less instant. It’s easy to be drawn in by their technological siren song, because a faceless assistant with a pleasing voice that exists to serve and can provide most any answer immediately is an exciting and attractive idea. Come up with something like that, and you can pretty much write the book on how it looks. At least, until public opinion or litigation makes you change your mind.
In seeking out an answer to this issue, more control seems like a good start. Physical solutions are the safest way, second only to not having an open mic in the first place. Most smart speakers have a mic mute button, but you’ll have to remember later why Alexa’s not answering you.
An easy way to kill the network connection would be nice, too. You already have the power to isolate your smart speaker(s) on their own network and give it the ol’ man-in-the-middle finger whenever you need to — but that requires basic network admin skills that many people don’t have. A software dashboard would be useful for disabling them for chunks of time without leaving the couch, so consider setting up your work hours as times when Siri, Cortana, and Okay Google are put into a cone of silence.
Of course, smart speakers aren’t the only ubiquitous products with microphones, so solving the consumer-created problems are just the start. The best solution to all of this nonsense may be to usher in an era of protective fashion, starting with bracelets that drown microphones in ultrasonic waves.
Accurate Dispensing Of Toilet Paper Will Get Us Through The Crisis
By Jenny List
As we enter our second week of official COVID-19-related lockdown where this is being written, it’s evident that there are some resources we will have to conserve to help get us through all this. Instead of just using all of something because we can nip out to the store and buy more, we have to look at what we’ve got and treat it as though it will have to get us through the next three months. It’s not always certain that on our infrequent trips to the supermarket they’ll have stocks of what we want.
A particular shortage has been of toilet paper. The news was full of footage showing people fighting for the last twelve-pack, and since early last month there has been none to be had for love nor money. To conserve stocks and save us from the desperate measures of having to cut the Daily Mail into squares and hang them on the wall, a technical solution is required. To this end I’ve created a computerised toilet roll dispenser which carefully controls the quantity of the precious sanitary product, in the hope of curbing its consumption to see us through the crisis.
In the midst of a full lockdown it’s difficult to secure immediate delivery of our usual maker essentials, so rather than send off for the controller boards I might have liked it has been necessary to make do with what I had. In the end I selected an older single board computer I had in a box under my bench. The Sinclair ZX81 has a single-core Z80 processor running at 3.25 MHz, dual-channel memory, a Ferranti GPU, and plenty of expansion possibilities from its black plastic case. I chose it because I could repurpose its thermal printer peripheral as a toilet paper printer, and because it has an easily wiped and hygienic membrane keyboard rather than a conventional one that could harbour germs.
Hardware wise I found I was fairly easily able to adapt a standard roll of Cushelle to the ZX printer, and was soon dispensing sheets with the following BASIC code.
10 REM TOILET PAPER PRINTER
20 FOR T=0 TO 44
30 LPRINT ""
40 NEXT T
50 LPRINT "---------- TEAR HERE -----------"
For now it’s working on the bench, but it will soon be mounted with a small portable TV as a monitor on the wall next to the toilet. Dispensing toilet paper will be as simple as typing RUN and hitting the ZX’s NEW LINE key, before watching as a sheet of toilet paper emerges magically from the printer. It’s the little hacks like this one that will be so useful in getting us through the crisis. After all, this Sinclair always has a square to spare.
As a writer, I have long harboured a dream that one day an editor will buy me a top-of-the-range audio analyser, and I can set up an audio test lab and write pieces debunking the spurious claims made by audiophiles, HiFi journalists, and the high-end audio industry about the quality of their products. Does that amp really lend an incisive sibilance to the broader soundstage, and can we back that up with some measurable figures rather than purple prose?
An Audio Playground You Didn’t Know You Had
Sadly Hackaday is not an audio magazine, and if Mike bought me an Audio Precision he’d have to satisfy all the other writers’ test equipment desires too, and who knows where that would end! So there will be no Hackaday audio lab — for now. But that doesn’t mean I can’t play around with audio analysis.
Last month we carried a write-up of a Supercon talk from Kate Temkin and Michael Ossmann, in which they reminded us that we have a cracking general purpose DSP playground right under our noses; GNU Radio isn’t just for radio. Once I’d seen the talk my audio analysis horizons were opened up considerably. Maybe that audio analyser wouldn’t be mine, but I could do some of the same job with GNU Radio.
It’s important to stress at this point that anything I can do on my bench will not remotely approach the quality of a professional audio analyser. But even if I can’t measure infinitesimal differences between very high-end audio circuitry, I can still measure enough to tell a good audio product from a bad one.
Making An Audio Analyser From A Software Defined Radio
For my ersatz audio analyser I decided to keep it pretty simple, and measure only the total harmonic distortion, or THD. Strictly speaking I’m measuring THD plus noise, but in the context of experimentation this does not concern me. THD is expressed as a percentage, and it’s generally best thought of as the percentage of the signal emerging from a device under test that is due to the distortion present in the device. Thus a theoretical perfect device has a THD of 0%. The simplest way to measure THD is to inject a single frequency on the device input, then to divide what remains on the output when that frequency is filtered out by the component of that frequency present on the output. This requires a set of extremely good filters, hard work in analogue circuitry but a simple task in GNU Radio.
The flowgraph I came up with is a pretty simple one: a low pass filter cuts off just above the injected frequency while a high pass one cuts in just above that to give me the harmonics. Then it’s a simple case of mathematics to derive my % THD reading.
I’m using opposite channels of my stereo sound card as input and output, and if I hook them directly together I retrieve a THD figure with a 1kHz input of 0.0024%. Thus I’ve measured the THD of a Dell soundcard, and while it’s not as bad as it could be, for comparison a unit pitched at audiophiles would boast an extra couple of leading zeros. But of course, I haven’t just measured the THD of the soundcard.
While in theory the all-digital signal path of GNU radio is distortion-free, in fact it introduces distortion of its own. There is quantisation distortion, and distortion induced by imperfections in the filters, and then of course there is noise coming from whatever else a computer running a multitasking desktop operating system is doing. A good example came when I took the screenshot of the flowgraph, immediately the THD jumped by a factor of ten for a short time. There is a really good reason why that professional audio analyser costs so much, and why we don’t use commodity soundcards to do the job instead.
Are Gold Cables Really Better?
Having an audio analyser to play with, albeit a not very good one, I cast around for a test subject to try with it. The obvious thing to do was to try a comparative test, and so to that end I dropped in a couple of orders for cables. Is there any truth in the claims of upmarket cable manufacturers, or is it simply snake oil designed to part the customer from their hard-earned?
I picked up a pair of 3 ft USB cables, extremely different ones from opposite ends of the market. One was a £4 ($5) Amazon Basics cable such as the one you are probably using to charge your phone, while the other was a £99 ($123) Gold Reference Series cable from Grundlagen Audio in Germany which its manufacturer claims through its gold plated Active Quantum Nanoparticle construction delivers an exceptionally low THD for digital audio transfers compared to that of conventional cables. What could I do, but hook each cable up in turn and give it a go?
Out of the box, both cables were of near-identical length and weight, but the Grundlagen was noticeably stiffer than the Amazon cable. Probably all that extra gold isn’t as flexible or something. I used the flowgraph linked above, but with a USB sink and source replacing the audio ones. I’d expect the THD figures to be significantly lower with this arrangement because of course I will have removed my poor-quality sound card from the equation. So in with the first cable, starting with the Amazon Basics cable in a loopback from USB port to USB port. Immediately I was able to measure a respectable THD at 1 kHz of 0.00014%, not surprising given the lack of a sound card. Very good, but what about the cable costing twenty times as much? In went the Grundlagen, and straight away the difference was clear with a 1 kHz THD of 0.00007%, half that of the Basics cable. Can you hear a difference when the number is that small? Probably not, but it does prove that a gold cable is better than a grey one even if they sound the same.
The folks at Grundlagen were kind enough to share a video with us showing how they manufacture their cables. Meanwhile should any of you wish to take the idea of an audio analyser in GNU Radio any further, we’re all ears.
Fail of the Week: How Not to Die of Boredom During Isolation
By Dan Maloney
They say you can’t actually die from boredom, but put a billion or so people into self-isolation, and someone is bound to say, “Hold my beer and watch this.” [Daniel Reardon]’s brush with failure, in the form of getting magnets stuck up his nose while trying to invent a facial touch reminder, probably wasn’t directly life-threatening, but it does underscore the need to be especially careful these days.
The story begins with good intentions and a small stack of neodymium magnets. [Daniel]’s idea for a sensor to warn one of impending face touches was solid: a necklace with magnetic sensors and wristbands studded with magnets. Sounds reasonable enough; one can easily see a compact system that sounds an alarm when a hand subconsciously crosses into the Danger Zone while going in for a scratch. Lacking any experience in circuits, though, [Daniel] was unable to get the thing working, so he started playing with the magnets instead. One thing led to another, and magnets were soon adorning his earlobes, and then his nostrils. Unfortunately, two magnets became locked on either side of his septum, as did two others meant to neutralize the pull of the first pair. So off [Daniel] went to the emergency department for a magnetectomy.
Of course it’s easy to laugh at someone’s misfortune, especially when self-inflicted. And the now-degaussed [Daniel] seems to be a good sport about the whole thing. But the important thing here is that we all do dumb things, and hackers need to be especially careful these days. We often work with sharp, pointy, sparky, toxic, or flammable things, and if we don’t keep our wits about us, we could easily end up in an ER somewhere. Not only does that risk unnecessary exposure to COVID-19, but it also takes medical resources away from people who need it more than you do.
By all means, we should be hacking away these idle hours. Even if it’s not in support of COVID-19 solutions, continuing to do what we do is key to our mental health and well-being. But we also need to be careful, to not stretch dangerously beyond our abilities, and to remember that the safety net that’s normally there to catch us is full of holes now.
Thanks to [gir.st] for the tip — you actually were the only one to send this in.
Empanada Becomes Impractical, Delicious Synth
By Lewin Day
Vegemite is an Australian staple – a rich, protein-filled sandwich spread with a strong salty flavor. It serves as a great way to add a little umami to any dish, which is the hottest open secret in Australian cuisine this decade. It also works as a servicable conductive paint, which [Alex] used to make this baked good into a musical device.
The basis of the device is a basic audio example sketch running on an Adafruit Circuit Playground Express. The code was tweaked to play a 7-note C major scale. The PCB was then attached to the empanada with toothpicks through each pad, with the baked good itself seemingly connected to the ground plane. The toothpicks through the pads were then coated with Vegemite, and another toothpick treated the same way and used as a stylus. By touching the toothpick to the empanada and one of the pads, the circuit is made, and a note is played.