sound

85 Articles

RFID Emulator + E-paper Badge Can Be Programmed With Sound

July 22, 2023 by 9 Comments

In a way, an e-paper display makes an excellent foundation for a reprogrammable RFID card. The display only needs power during a refresh, and 125 kHz RFID tags are passive in the sense that the power for the RFID transaction comes from the reader itself. [Georgi Gerganov] has put those together in the GGtag, an open-source project for a 3.52″ e-paper badge with a trick or two up its sleeve.

One clever function is that it is programmable with sound, a feature built off another project of [Georgi]’s called ggwave, a data-to-sound (and vice-versa) framework that has been ported to just about every hardware platform one cares to imagine — including mobile phones — and can reliably send data through the air.

Transmitting data over sound is limited in throughput but has a number of advantages, not least of which is the huge range of compatible devices. There’s a web-based tool for programming the GGtag with sound available at ggtag.io that will give you a preview and let you hear how it works. The data encoding method gives transmissions a charming beep-boop quality that’s a bit reminiscent of an analog modem handshake. GGtag can also be programmed over USB serial, a faster (but somewhat less exciting) option.

The project’s GitHub repository contains GGtag’s code and technical details, and the CrowdSupply project is in the works for anyone who would prefer to buy one once they become available.

Listening To Bats As They Search For Food

July 14, 2023 by 14 Comments

The range of human hearing goes up to about 20 kilohertz, which is fine for our purposes, but is pretty poor compared to plenty of other animal species. Dogs famously can hear up to about 60 kHz, and dolphins are known to distinguish sounds up to 100 kHz. But for extremely high frequencies we’ll want to take a step into the world of bats. Some use echolocation to locate each other and their food sources, and bats like the pipistrelle can listen in to sounds up to 350 kHz. To listen to them you’ll need a device like the π*pistrelle. (Ed Note: a better explanation is available at the project’s website.)

The original implementation of the bat detector was based on a Raspberry Pi Pico, from which it gets its name. But there have been several improvements on it in the years since it was first developed. The latest can detect bats when it hears their 350 kHz sonar calls thanks to an ultrasonic microphone and op amp. The device then records the bat sounds and then either heterodynes the sound down or time-expands it to human-audible range so the calls can actually be heard. There’s an LED display on the board as well as three input buttons, but an iOS companion app is available to interact with the device as well.

If you want to know for sure which species is flying around at night, you can use machine learning to help figure that out.

Taking Mechanical Keyboard Sounds To The Next Level

July 13, 2023 by 10 Comments

When it comes to mechanical keyboards, there’s no end to the amount of customization that can be done. The size and layout of the keyboard is the first thing to figure out, and then switches, keycaps, and then a bunch of other customizations inside the keyboard like the mounting plate and whether or not to add foam strips and other sound- and vibration-deadening features. Of course some prefer to go the other direction with it as well, omitting the foam and installing keys with a more noticeable click, and still others go even further than that by building a separate machine to make their keyboard activity as disruptive as it could possibly be.

This started as a joke among [ac2ev] and some coworkers, who were already teasing about the distinct sound of the mechanical keyboard. This machine, based on a Teensy microcontroller, sits between any USB keyboard and its host computer, intercepting keystrokes and using a small solenoid to tap on a block of wood every time a keystroke is detected. There’s also a bell inside that rings when the enter key is pressed, similar to the return carriage notification for typewriters, and as an additional touch an audio amplifier with attached speaker plays the Mario power-up sound whenever the caps lock key is pressed.

[ac2ev] notes that this could be pushed to the extreme by running a much larger solenoid powered by mains electricity, but since this was more of a proof-of-concept demonstration for some coworkers the smaller solenoid was used instead. The source code for the build can be found on the project’s GitHub page and there’s also a video of this machine in action here as well. Be careful with noisy mechanical keyboards, though, as the sounds the keys produce can sometimes be decoded to determine what the user is typing.

Using Sonar To Measure Traffic Speeds

June 19, 2023 by 21 Comments

One of the most common ways of measuring the speed of a vehicle is by using radar, which typically involves generating radio waves, directing them at a moving vehicle, and measuring the various ways that they return to the device. This is a tried-and-true method, but can be expensive and technically complex. [GeeDub] wanted an easier way of measuring vehicles passing by his home, so he switched to using sonar instead to measure speeds based on the sounds the cars generate themselves.

The method he is using is similar to passive sonar in submarines, which can locate objects underwater based on the sounds they produce. After a false start attempting to measure Doppler shift, he switched to time correlation using two microphones, essentially using stereo audio input to detect subtle differences in arrival times of various sounds to detect the positions of passing vehicles. Doing this fast enough and extrapolating the data gathered, speed information can be calculated. For the data gathering and calculation, [GeeDub] is using a Raspberry Pi to help keep costs down, and some further configuration of the microphones and their power supplies were also needed to ensure quality audio was gathered.

With the system in place in a window, it detected around 9,000 vehicles over a three-day period. The software generates a normal distribution of vehicle speeds for this time, with the distribution centered on around 35 MPH, slightly above the posted speed limit of 30. As long as there’s a clear line of sight to the road using this system it’s just as effective as some other passive systems we’ve seen to measure vehicle speed. Of course, active speed measurement systems are not out of the realm of possibility if you’re willing to spend a little more.

Mechanical Keyboard As Travel Saxophone

March 14, 2023 by 9 Comments

Those who play larger musical instruments, things like drums, piano, harp, tuba, upright bass, or Zeusaphone, know well the challenges of simply transporting their chosen instrument to band practice, a symphony hall, or local watering hole. Even those playing more manageably-sized instruments may have similar troubles at some point especially when traveling where luggage space is at a premium like on an airplane. That’s why [jcard0na] built this electronic saxophone, designed to be as small as possible.

Known as the “haxophone”, the musical instrument eschews the vibrating column of air typical of woodwind instruments in favor of an electronic substitute. Based around the Raspberry Pi, the device consists of a custom HAT with a number of mechanical keyboard switches arrayed in a way close enough to the layout of a standard saxophone that saxophonists will be able to intuitively and easily play. Two pieces of software run on the Pi to replicate the musical instrument, one that detects the player’s breaths and key presses, and another that synthesizes this information into sound.

While [jcard0na] notes that this will never replicate the depth and feel of a real instrument, it does accomplish its design goal of being much more easily transportable than all but the most soprano of true saxophones. As a musical project it’s an excellent example of good design as well, much like this set of electronic drums with a similar design goal of portability.

A small electronic board next to colorful stylized speaker

Soundscape Sculpture Is Pleasing Art For Your Ears

January 18, 2023 by 4 Comments

Artist and self-described “maker of objects” [Daric Gill] is sharing some of the world’s most pleasing and acoustically interesting soundscapes with museum patrons in his latest work, ‘The Memory Machine: Sound‘.

Now featured at the Center of Science and Industry museum, the interactive stereo soundscape generator resembles three decorated ‘tree trunks’, suspended high above the exhibition floor. When visitors approach the artwork, they are treated to a randomly selected soundscape sample.

The build, which is described in blog form here, teases just some of the sixty soundscape samples that can be heard. These include the noisy chattering of crowds underneath the Eiffel Tower in Paris, the mellow melodies of a meadow high in the Swiss Alps, and the pumping atmosphere of a baseball match played in Yankee Stadium, New York City.

Only the middle trunk reveals the electronic soul of the installation – an Adafruit M4 Feather Express, Music Maker Featherwing and a motion sensor. The flanking trunks house the speakers and amplifier. The motion sensor triggers the microcontroller, which then plays a randomly selected sample from an SD card.

[Daric] went to great lengths to reuse discarded materials, and even cannibalized parts from other sculptures to see his vision through. This focus underpins a substantial amount of woodworking and machining that went into this build, so the full video is certainly worth a watch to see the whole project come together.

Make sure to check out our coverage of other funky installations, like this mesmerizing ceiling decoration.

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I’ve Got Two Turntables And A Laser Engraver

November 27, 2022 by 29 Comments

Digital media provides us with a lot of advantages. For something like recording and playing back music, digital copies don’t degrade, they can have arbitrarily high quality, and they can be played in a number of different ways including through digital streaming services. That being said, a number of people don’t feel like the digital experience is as faithful to the original sound as it could be and opt for analog methods instead. Creating analog copies of music is a much tougher matter though, as [Marco] demonstrates by using a laser engraver to produce vinyl records.

[Marco] started this month-long project by assembling and calibrating the laser engraver. It has fine enough resolution to encode analog data onto a piece of vinyl, but he had to create the software. The first step was to generate the audio sample, then process it through a filter to remove some of the unwanted frequencies. From there, the waveform gets made into a spiral, accounting for the changing speed of the needle on the record as it moves to the center. Then the data is finally ready to be sent to the laser engraver.

[Marco] did practice a few times using wood with excellent success before moving on to vinyl, and after some calibration of the laser engraver he has a nearly flawless 45 rpm record ready to hit the turntable. It’s an excellent watch if not for anything than seeing a working wood record. We’ve actually seen a similar project before (without the wood prototyping), and one to play records from an image, but it’s been quite a while.

Thanks to [ZioTibia81] for the tip!

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