Remoticon Video: Making Microphones And Finding Sound

December 8, 2020 by Mike Szczys 14 Comments

A yogurt lid and embroidery hoop are key components in building this microphone. It’s a super low tech, entry-level project to get into “found sound” and exactly what is needed to start hacking around in the audio world. This workshop presented by Helen Leigh and Robyn Hails shows you how to build a simple microphone and use it as the electronic gateway to all kinds of audio shenanigans.

Key to this build are the piezo element and an amp to process the signals it generates. All other materials are common around most households, but put them together as shown in this live hands-on seminar from the 2020 Hackaday Remoticon, and I think you’ll surprise yourself with how good the thing sounds!

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Hackaday Links: November 22, 2020

November 22, 2020 by Dan Maloney 6 Comments

Remember DSRC? If the initialism doesn’t ring a bell, don’t worry — Dedicated Short-Range Communications, a radio service intended to let cars in traffic talk to each other, never really caught on. Back in 1999, when the Federal Communications Commission set aside 75 MHz of spectrum in the 5.9-GHz band, it probably seemed like a good idea — after all, the flying cars of the future would surely need a way to communicate with each other. Only about 15,000 vehicles in the US have DSRC, and so the FCC decided to snatch back the whole 75-MHz slice and reallocate it. The lower 45 MHz will be tacked onto the existing unlicensed 5.8-GHz band where WiFi now lives, providing interesting opportunities in wireless networking. Fans of chatty cars need not fret, though — the upper 30 MHz block is being reallocated to a different Intelligent Transportation System Service called C-V2X, for Cellular Vehicle to Everything, which by its name alone is far cooler and therefore more likely to succeed.

NASA keeps dropping cool teasers of the Mars 2020 mission as the package containing the Perseverance rover hurtles across space on its way to a February rendezvous with the Red Planet. The latest: you can listen to the faint sounds the rover is making as it gets ready for its date with destiny. While we’ve heard sounds from Mars before — the InSight lander used its seismometer to record the Martian wind — Perseverance is the first Mars rover equipped with actual microphones. It’s pretty neat to hear the faint whirring of the rover’s thermal management system pump doing its thing in interplanetary space, and even cooler to think that we’ll soon hear what it sounds like to land on Mars.

Speaking of space, back at the beginning of 2020 — you know, a couple of million years ago — we kicked off the Hack Chat series by talking with Alberto Caballero about his “Habitable Exoplanets” project, a crowd-sourced search for “Earth 2.0”. We found it fascinating that amateur astronomers using off-the-shelf gear could detect the subtle signs of planets orbiting stars half a galaxy away. We’ve kept in touch with Alberto since then, and he recently tipped us off to his new SETI Project. Following the citizen-science model of the Habitable Exoplanets project, Alberto is looking to recruit amateur radio astronomers willing to turn their antennas in the direction of stars similar to the Sun, where it just might be possible for intelligent life to have formed. Check out the PDF summary of the project which includes the modest technical requirements for getting in on the SETI action.

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Robots Can Finally Answer, Are You Talking To Me?

November 8, 2020 by Matthew Carlson 25 Comments

Voice Assistants, love them, or hate them, are becoming more and more commonplace. One problem for voice assistants is the situation of multiple devices listening in the same place. When a command is given, which device should answer? Researchers at CMU’s Future Interfaces Group [Karan Ahuja], [Andy Kong], [Mayank Goel], and [Chris Harrison] have an answer; smart assistants should try to infer if the user is facing the device they want to talk to. They call it direction-of-voice or DoV.

Currently, smart assistants use a simple race to see who heard it first. The reasoning is that the device you are closest to will likely hear it first. However, in situations with echos or when you’re equidistant from multiple devices, the outcome can seem arbitrary to a user.

The implementation of DoV uses an Extra-Trees Classifier from the python sklearn toolkit. Several other machine learning algorithms were considered, but ultimately efficiency won out and Extra-Trees was selected. Another interesting facet of the research was determining what facing really means. The team had humans ‘listeners’ stand in for smart assistants. A ‘talker’ would speak the key phrase while the ‘listener’ determined if the talker was facing them or not. Based on their definition of facing, the system can determine if someone is facing the device with 90% accuracy that rises to 93% with per-room calibration.

Their algorithm as well as the data they collected has been open-sourced on GitHub. Perhaps when you’re building your own voice assistant, you can incorporate DoV to improve wake-word accuracy.

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Building A Top-Notch Electret Microphone

November 2, 2020 by Lewin Day 25 Comments

Electret microphones are capable of high-quality output, and are prized for their smooth frequency response. However, unlike other types, they can’t simply be plugged directly into a mixing desk. Instead, they require special high-impedence circuitry to extract the audio signal for recording. [DJJules] is a big fan of these microphones, and decided to build a high-quality, easy to use circuit that he has shared with the community.

The goal of the project was to create a circuit to match the TSB2555B electret capsule that could be used with phantom power, and that could be built with easily obtainable parts. [DJJules] had used FETs in the past, but grew tired of routinely having to hunt for obsolete parts. Instead, this design relies on a dual OPA1642 op-amp, with its low quiescent current meaning it’s perfect for running off phantom power. This means the microphone needs no batteries, and using a dual op-amp enables the circuit to properly drive a balanced audio connection.

The circuit is designed to fit inside a common BM700 or BM800 microphone body, and the PCB can be ordered from PCBWay for those interested in building their own. There’s also a saddle on Shapeways that’s designed to neatly mount the electret capsule within the housing.

The final results are impressive, and this project would make a great entry into the DIY microphone space for anyone eager to start building their own gear. Of course, there are simpler builds if you’re looking for an easier way to get started. Video after the break.

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Push Pedal For Privacy

September 29, 2020 by Brian McEvoy 17 Comments

Many of us in the secret Hackaday lair use gaming hardware at our work desks because it is reliable and performs well. We are not alone, and maybe you are reading this on your coffee break over a 20-button mouse. We wager that [Thiago Ribeiro de Azeredo] has this mindset because he converted some old analog gaming pedals into teleconferencing tools for his home office. Now that he is not racing to the office, he has to take a lot of computer calls, and he must quickly and covertly mute his microphone when his howling son tries to take the stage.

The pedals were gathering dust when he started working from home, but they are unretired for the upgrade. Inside, there is no mystery, just a couple of spring-loaded variable resistors, so he adds an Arduino Nano a couple of 4.7 kΩ resistors to create a voltage divider. The Nano doesn’t have native Human Interface Device (HID) functionality, so a Python script receives the serial port signals and toggles an application bar notification so he can see the microphone status. With two pedals, he can press-to-talk or lock his microphone on and off. We have to wonder, did he write the software during a meeting?

We love the idea of controlling our battle stations with our feet or seeing a bunch of RGB keyboards used as a low-res display.

Wireless Sax Mic Done On The Cheap

August 15, 2020 by Lewin Day 7 Comments

Sometimes, economies of scale don’t work in our favor. While guitarists and singers will find themselves well catered to by the accessories market, players of fancier, less popular instruments will often have to dig deeper in their pockets to get what they need. [Henry Goh] found himself in need of a saxophone mic. However, off-the-shelf solutions were a touch expensive, and thus he decided he could probably whip something up himself. (Video, embedded below.)

Parts of a saxophone, for the uninitiated. The microphone should be placed a good distance from the center of the bell to pick up the best sound.

It’s a simple solution, one that we could imagine any maker quickly whipping up with junkbox parts. Not one to skimp on quality, [Henry] picked a Rode Wireless Go paired with a lavalier mic for a quality wireless microphone solution. The real problem would be mounting the device, intended to be worn on a shirt, to the right position in front of the saxophone’s bell.

To achieve this, most dedicated sax mics used a bendable arm to allow the position to be readily changed. Instead, [Henry] whipped up some mounts on the 3D printer that would allow him to mount the Rode wireless mic hardware on an bendy Energizer LED torch. The torch even comes with a clamp allowing it to be easily attached to the instrument, making fitment a cinch.

[Henry] estimates the solution saved him up to $800 SGD. The final result is cost effective, and gives quality easily good enough for amateur and community performances. As a bonus, the hack is non-destructive, meaning you can repurpose the lavalier mic for other work as needed.

We love a good hack on the cheap, and it’s something we see all the time in the music scene. This guitar build is a great example of the form.

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Get The Party Started With A Mesh WiFi Light Show

June 26, 2020 by Sven Gregori 1 Comment

Wildly blinking LEDs may not be the ideal lighting for the average office environment, but they’ll surely spice up any party. And since a party without music is just a meeting, having both synced up is a great way to set the mood. Sure, you could simply roll out your standard LED strip instead, but that gets a bit boring, and also a bit tricky if you want to light up several places the same way. [Gerrit] might have built the perfect solution though, with his (mu)sic (R)eactive (Li)ghts, or muRLi, which are a set of individual lights that synchronize a programmable pattern over WiFi.

The system consists of muRLi itself as the base station that defines and sends the light pattern through WebSockets, and several muRLi Nodes that house a set of WS2812B LEDs to receive and display it. Both are built around a Wemos D1 Mini configured to set up a WiFi mesh network, and depending what’s in reach, the nodes connect either to the base station or other nodes, giving the system definitely enough reach for any location size. The music is picked up by a MAX4466-amplified microphone inside the base station — adding some more flexibility to positioning the system — and analyzed for volume and audio spectrum, which is also shown on an OLED.

The best part however is how the light patterns are programmed. Instead of hard-coding it into the firmware, [Gerrit] went for a modular approach with little ROM cartridges to plug into the muRLi base station. The cartridge itself contains just an I2C EEPROM, storing JavaScript code that is interpreted by the firmware using mJS. The scripts have access to the analyzed audio data and amount of LEDs within the network, and can dynamically generate the patterns as needed that way. Everything is neatly housed in 3D-printed enclosures, with all the design and source files available on the project’s GitHub page — but see for yourself in the video after the break.

If you don’t care about the wireless part but enjoy light synced up with music, have a look at a plain MIDI solution for that. As for [Gerrit], we’re definitely looking forward to seeing his next endeavor one day, since we also enjoyed his last one.

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