sound

85 Articles

Audio On Pi: Here Are Your Options

August 12, 2024 by 36 Comments

There are a ton of fun Raspberry Pi and Linux projects that require audio output – music players, talking robots, game consoles and arcades, intelligent assistants, mesh network walkie-talkies, and much more! There’s no shortage of Pi-based iPods out there, and my humble opinion is that we still could use more of them.

To help you in figuring out your projects, let’s talk about all the ways you can use to get audio out of a Pi or a similar SBC. Not all of them are immediately obvious and you ought to know the ropes before you implement one of them and get unpleasantly surprised by a problem you didn’t foresee. I can count at least five ways, and they don’t even include a GPIO-connected buzzer!

Let’s rank the different audio output methods, zoning in on things like their power consumption, and sort them by ease of implementation, and we’ll talk a bit about audio input options while we’re at it.

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Swapping Vinyl For Cardboard With This ESP32 Turntable

June 30, 2024 by 15 Comments

Cardboard is a surprisingly durable material, especially in its corrugated form. It’s extremely lightweight for its strength, is easy to work, can be folded and formed into almost any shape, is incredibly inexpensive, and when it has done its duty it can be recycled back into more paper. For these reasons, it’s often used in packaging material but it can be used to build all kinds of things outside of ensuring that products arrive at their locations safely. This working cardboard record player is one example.

While the turntable doesn’t have working records in the sense that the music is etched into them like vinyl, each has its own RFID chip embedded that allows the ESP32 in the turntable’s body to identify them. Each record corresponds to a song stored on an SD card that instructs the ESP32 to play the appropriate song. It also takes care of spinning the record itself with a small stepper motor. There are a few other details on this build that tie it together too, including a movable needle arm held on with a magnet and a volume slider.

As far as a building material goes, cardboard is fairly underrated in our opinion. Besides small projects like this turntable, we’ve also seen it work as the foundation for a computer, and it even has the strength and durability to be built into a wall or even used as shelving material. And, of course, it’s a great material to use when prototyping new designs.

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Reggaeton-Be-Gone Disconnects Obnoxious Bluetooth Speakers

February 23, 2024 by 29 Comments

If you’re currently living outside of a Spanish-speaking country, it’s possible you’ve only heard of the music genre Reggaeton in passing, if at all. In places with large Spanish populations, though, it would be more surprising if you hadn’t heard it. It’s so popular especially in the Carribean and Latin America that it’s gotten on the nerves of some, most notably [Roni] whose neighbor might not do anything else but listen to this style of music, which can be heard through the walls. To solve the problem [Roni] is now introducing the Reggaeton-Be-Gone. (Google Translate from Spanish)

Inspired by the TV-B-Gone devices which purported to be able to turn off annoying TVs in bars, restaurants, and other places, this device can listen to music being played in the surrounding area and identify whether or not it is hearing Reggaeton. It does this using machine learning, taking samples of the audio it hears and making decisions based on a trained model. When the software, running on a Raspberry Pi, makes a positive identification of one of these songs, it looks for Bluetooth devices in the area and attempts to communicate with them in a number of ways, hopefully rapidly enough to disrupt their intended connections.

In testing with [Roni]’s neighbor, the device seems to show promise although it doesn’t completely disconnect the speaker from its host, instead only interfering with it enough for the neighbor to change locations. Clearly it merits further testing, and possibly other models trained for people who use Bluetooth speakers when skiing, hiking, or working out. Eventually the code will be posted to this GitHub page, but until then it’s not the only way to interfere with your neighbor’s annoying stereo.

Thanks to [BaldPower] and [Alfredo] for the tips!

Localizing Fireworks Launches With A Raspberry Pi

December 30, 2023 by 103 Comments

If you have multiple microphones in known locations, and can determine the time a sound arrives at each one, you can actually determine the location that sound is coming from. This technique is referred to as sound localization via time difference of arrival. [Kim Hendrikse] decided to put the technique to good use to track down the location of illicit fireworks launches.

The build is based on the Raspberry Pi, with [Kim] developing an “autonomous recording unit” complete with GPS module for determining their location and keeping everything time synchronized. By deploying a number of these units, spread out over some distance, it’s possible to localize loud sounds based on the time stamps they show up in the recording on each unit.

Early testing took place with an air horn and four recording units. [Kim] found that the technique works best for sounds made within the polygon.  Determining the location was achieved with a sound investigation tool called Raven Lite, developed by Cornell University. The process is very manual, involving hunting for peaks in sound files, but we’d love to see a version that automated comparing sound peaks across many disparate recording units. In any case, it worked incredibly well for [Kim] in practice. Later testing with friends and a network of six recorders spread over Limburg, Netherlands, [Kim] was later able to localize fireworks launches with an accuracy down to a few meters.

Similar techniques are used to locate gunshots, and can work well with pretty much any loud noise that’s heard over a great distance. If you’ve been using your hacker skills to do similar investigative work, don’t hesitate to let us know on the tipsline!

Digital Bike Horn Will Play Custom Sounds, Please Be Tasteful

December 23, 2023 by 19 Comments

When you’re out riding your bike, a horn can be a useful warning device to other road users and pedestrians alike. It can also be a source of fun and amusement, or annoyance, depending on the sounds it makes and how you use it. For the ultimate flexibility, you might like this digital bicycle horn that offers customizable sounds, as developed by [gokux].

The build has attractive two-tone components, consisting of a button pad for playing four sounds, and a sound module with a 3 watt speaker and battery pack. A Seeed Studio XIAO SAMD21 is the heart of the operation, with the microcontroller paired with a DFPlayer Mini which handles sound duties. When one of the four buttons is pressed, the microcontroller loads the relevant sound off an SD card, and plays it out over the speaker. For power, the build uses a lithium rechargeable battery with a healthy 1200 mAh capacity, which can be readily recharged thanks to a TP4056 charger module with a USB-C port.

It’s a nifty little build, and we love the Metal Gear Solid sounds. Though, we do wonder just how audible that 3 watt speaker is. If it proves inadequate, you could always step up to a much larger driver paired with a hefty audio amp if you so desire.

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Low-Cost Electret Microphone Preamplifiers

October 16, 2023 by 8 Comments

Before the invention of microelectromechanical system (MEMS) microphones, almost all microphones in cell phones and other electronics were a type of condenser microphone called the electret microphone. The fact that this type of microphone is cheap and easy enough to place into consumer electronics doesn’t mean they’re all low quality, though. Electret microphones can have a number of qualities that make them desirable for use recording speech or music, so if you have a struggling artist friend like [fvfilippetti] has who needs an inexpensive way to bring one to life, take a look at this electret microphone pre-amp.

The main goal of the project is to enhance the performance of these microphones specifically in high sound pressure level (SPL) scenarios. In these situations issues of saturation and distortion often occur. The preampl design incorporates feedback loops and an AD797 opamp to reduce distortion, increase gain, and maintain low noise levels. It also includes an output voltage limiter using diodes to protect against input overload and can adjust gain. The circuit’s topology is designed to minimize distortion, particularly in these high SPL situations.

Real-world testing of the preamp confirms its ability to handle high SPL and deliver low distortion, making it a cost-effective solution for improving the performance of electret microphones like these. If you want to go even deeper into the weeds of designing and building electret microphones and their supporting circuitry, take a look at this build which discusses some other design considerations for these types of devices.

Get MOST Into Your Pi

August 3, 2023 by 15 Comments

When looking the modify a passenger vehicle, the Controller Area Network (CAN) bus is a pretty easy target. In modern vehicles it has access to most of the on-board systems — everything from the climate control to the instrument cluster and often even the throttle, braking, and steering systems. With as versatile as the CAN bus is, though, it’s not the right tool for every job. There’s also the Media Oriented Systems Transport (MOST) bus which is increasingly found in automotive systems to handle multimedia such as streaming music to the stereo. To access that system you’ll need to approach it slightly differently as [Rhys] demonstrates.

[Rhys] has been working on replacing the dated head unit in his Jaguar, and began by investigating the CAN bus. He got almost everything working with replacement hardware except the stereo, which is where the MOST bus comes into play. It provides a much higher bandwidth than the CAN bus can accommodate but with almost no documentation it was difficult to interact with at first. With the help of a Raspberry Pi and a lot of testing he is able to get the stereo working again with a much more modern-looking touchscreen for control. It is also able to do things like change CDs in the car’s CD player, gather song information from the CD to display on the panel, and can perform other functions of the infotainment center.

For more detailed information on the MOST bus, [Rhys] also maintains a website where he puts his discoveries and other information he finds about this system. Unfortunately car stereo systems in modern vehicles can get pretty complicated these days, but adapting car stereos in older vehicles to modern technology carries some interesting challenges as well.

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