Ultrasonic Sound Gun Precisely Aims Your Music

April 30, 2020 by Moritz v. Sivers 25 Comments

When listening to music you sometimes cannot avoid the situation where other people get annoyed because they feel it disrupts their important doings or they do not share your taste in avant-garde doom metal. Of course one could just use headphones. But a hackier way would be to build a parametric speaker that focuses soundwaves into a narrow beam like [Shane] did with this ultrasonic sound gun.

As the directivity of a soundwave depends on the size of the source and its frequency, a directed beam can practically only be achieved with ultrasound. Even though we are not able to perceive frequencies above ~20 kHz, the nonlinear properties of air make it possible to hear the audio modulated onto an ultrasonic carrier signal. For his sound gun [Shane] was inspired by another parametric speaker project. It took him some time to get the 555 timer circuit oscillating at the right frequency and he fried a cheap Bluetooth audio module while trying to increase the output volume but in the end, he managed to get everything working. As the project name suggests, he also 3D printed a gun-shaped enclosure. The video below shows that the sound from the gun behaves really similar to a beam of light and can, for example, be bounced off other objects.

If you are looking for other inspiration there is a whole list of cool ultrasonic projects from distance sensors to acoustic levitation.

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Slippy Slapper Uselessly Uses All The Arduinos

March 13, 2020 by Kristina Panos 8 Comments

Want to take that annoyingly productive coworker down a notch? Yeah, us too. How dare they get so much done and be so happy about it? How is it possible that they can bang on that keyboard all day when you struggle to string together an email?

The Slippy Slapper is a useless machine that turns people into useless machines using tactics like endless distraction and mild physical violence. It presses your buttons by asking them to press buttons for no reason other than killing their productivity. When they try to walk away, guess what? That’s another slappin’. Slippy Slapper would enrage us by proxy if he weren’t so dang cute.

You’re right, you don’t need an Arduino for this. For peak inefficiency and power consumption, you actually need four of them. One acts as the master, and bases its commands to the other three on the feedback it gets from Slippy’s ultrasonic nostrils. The other three control the slappin’ servos, the speakers, and reading WAV files off of the SD card. Slap your way past the break to see Slippy Slapper’s slapstick demo.

Need to annoy a group of coworkers all at once? Slip a big bank of useless machines into the conference room while it’s being set up.

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Death To All Coca Cola Cans With This Miniature Arduino Powered Cannon

December 8, 2019 by Gerrit Coetzee 8 Comments

[MJKZZ] sends in this entertaining little tutorial on building a small automated cannon out of a syringe.

He starts the build off by modifying an arc lighter, the fancy kind one might use to light a fire on a windy day, so that it can be controlled by a micro-controller. The arc is moved to the needle end of the syringe with a careful application of wires and hot glue. When the syringe is filled with a bit of alcohol and the original plunger is pressed back in a small spark will send it flying back out in a very satisfying fashion.

Of course it wouldn’t be a proper hack without an Arduino added on for no reason other than the joy of doing so. [MKJZZ] adds an ultrasonic sensor into the mix which, when triggered appropriately by an invading object fires the arc lighter using a reed relay.

He demonstrates the build by eliminating an intruding coke can on his work bench. You can see it in the video after the break. All in all a very fun hack.

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Behold A 3D Display, Thanks To A Speeding Foam Ball

November 19, 2019 by Donald Papp 15 Comments

We’ve seen 3D image projection tried in a variety of different ways, but this is a new one to us. This volumetric display by Interact Lab of the University of Sussex creates a 3D image by projecting light onto a tiny foam ball, which zips around in the air fast enough to create a persistence of vision effect. (Video, embedded below.) How is this achieved? With a large array of ultrasonic transducers, performing what researchers call ‘acoustic trapping’.

This is the same principle behind acoustic levitation devices which demonstrate how lightweight objects (like tiny polystyrene foam balls) can be made to defy gravity. But this 3D display is capable of not only moving the object in 3D space, but doing so at a high enough speed and with enough control to produce a persistence of vision effect. The abstract for their (as yet unreleased) paper claims the trapped ball can be moved at speeds of up to several meters per second.

It has a few other tricks up its sleeve, too. The array is capable of simultaneously creating sounds as well as providing a limited form of tactile feedback by letting a user touch areas of high and low air pressure created by the transducers. These areas can’t be the same ones being occupied by the speeding ball, of course, but it’s a neat trick. Check out the video below for a demonstration.
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Aging Alcohol In 30 Minutes

November 14, 2019 by Lewin Day 38 Comments

Many alcoholic beverages are aged in barrels for long periods of time. The aim is to impart flavors from the wood of the barrel into the liquid, and allow a whole host of chemical reactions to happen, changing the character of the taste. However, this takes time, and time is money. There’s potentially a faster way, however, and [The Thought Emporium] set out to investigate.

Inspired by several research papers, the goal was to examine whether using ultrasound to agitate these fluids could speed the aging process. Initial tests consisted of artificially aging milk, apple cider, and vodka in a small ultrasonic jewelry cleaner for 30 minutes, with cognac chips for flavor. Results were positive amongst the tasters, with the vodka in particular showing a marked color change from the process. A later test expanded the types of wood chip and beverages under test. Results were more mixed, but with a small sample size of tasters, it’s to be expected.

While taste is subjective, there were definite visible results from the aging process. It’s a technique that’s being explored by industry, too. We’ve seen hackers brew up plenty of tasty beverages before, too – often with a little automation thrown in Video after the break.

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Worried About Bats In Your Belfry? A Tale Of Two Bat Detectors

October 17, 2019 by Pat Whetman 33 Comments

As somebody who loves technology and wildlife and also needs to develop an old farmhouse, going down the bat detector rabbit hole was a journey hard to resist. Bats are ideal animals for hackers to monitor as they emit ultrasonic frequencies from their mouths and noses to communicate with each other, detect their prey and navigate their way around obstacles such as trees — all done in pitch black darkness. On a slight downside, many species just love to make their homes in derelict buildings and, being protected here in the EU, developers need to make a rigorous survey to ensure as best as possible that there are no bats roosting in the site.

Obviously, the authorities require a professional independent survey, but there’s still plenty of opportunity for hacker participation by performing a ‘pre-survey’. Finding bat roosts with DIY detectors will tell us immediately if there is a problem, and give us a head start on rethinking our plans.

As can be expected, bat detectors come in all shapes and sizes, using various electrickery techniques to make them cheaper to build or easier to use. There are four different techniques most popularly used in bat detectors.

Heterodyne: rather like tuning a radio, pitch is reduced without slowing the call down.
Time expansion: chunks of data are slowed down to human audible frequencies.
Frequency division: uses a digital counter IC to divide the frequency down in real time.
Full spectrum: the full acoustic spectrum is recorded as a wav file.

Fortunately, recent advances in technology have now enabled manufacturers to produce relatively cheap full spectrum devices, which give the best resolution and the best chances of identifying the actual bat species.

DIY bat detectors tend to be of the frequency division type and are great for helping spot bats emerging from buildings. An audible noise from a speaker or headphones can prompt us to confirm that the fleeting black shape that we glimpsed was actually a bat and not a moth in the foreground. I used one of these detectors in conjunction with a video recorder to confirm that a bat was indeed NOT exiting from an old chimney pot. Phew!

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