We pride ourselves on knowing the proper terms for everyday things: aglet, glabella, borborygmi, ampersands. But we have to confess to never having heard of a “fipple” before finding this interesting MIDI-controlled slide whistle, where we learned that the mouthpiece of a penny whistle or a recorder is known as a fipple. The more you know.
This lesson comes to us by way of a Twitter post by [The Mixed SIgnal], which showed off the finished mechanism in a short video and not much else. We couldn’t leave that alone, so we reached out for more information and were happy to find that [The Mixed SIgnal] quickly posted a build log on Hackaday.io as well as the build video below.
The slide whistle is a homebrew version of the kind we’ve all probably annoyed our parents with at one time or another, with a 3D-printed fipple (!) and piston, both of which go into a PVC tube. Air is supplied to the pipe with a small centrifugal blower, while a 3D-printed rack and pinion gear of unusual proportions moves the piston back and forth. An Arduino Due with a CNC shield controls the single stepper motor. The crude glissandos of this primitive wind instrument honestly are a little on the quiet side, especially given the racket the stepper and rack and pinion make when queuing up a new note. Perhaps it needs more fipple.
[Dr. Suess] created memorable books with minimal words and bright artwork. He inspired children and adults alike, and one of them, [Len], grew up to create wind instruments for the Bellowphone channel on YouTube. Behind the whimsy of his creations is significant engineering, and this time, we get to see the construction of a fipple. The video is also shown after the break. Even though fipple sounds like a word [Dr. Suess] would have coined, it is a legitimate musical term that means a whistle-like mouthpiece. In this case, it blows air across glass jars to create the sound for [Len]’s bottle organ. Check out the second video below for a performance from The Magic Flute.
[Len] uses clear rigid PVC for the fipples and a custom forming die to shape them while they are soft. The rest is precision hand-tool work with a razor saw, hand file, and wet-dry sandpaper. Once complete, the fipple looks like any musical instrument part produced by exacting construction techniques. Making a mouthpiece is one thing, but if it is not directed correctly it will not make any sound, so we also learn how to turn steel strapping into an organ bottle assembly. If you add some tubing and rubber squeeze balls, you can make your own instrument.
Late last year, artist [Steve Messam]’s project “Whistle” involved 16 steam engine whistles around Newcastle that would fire at different parts of the day over three months. The goal of the project was bring back the distinctive sound of the train whistles which used to be fixture of daily life, and to do so as authentically as possible. [Steve] has shared details on the construction and testing of the whistles, which as it turns out was a far more complex task than one might expect. The installation made use of modern technology like Raspberry Pi and cellular data networks, but when it came to manufacturing the whistles themselves the tried and true ways were best: casting in brass before machining on a lathe to finish.
The original whistles are a peek into a different era. The bell type whistle has three major components: a large bell at the top, a cup at the base, and a central column through which steam is piped. These whistles were usually made by apprentices, as they required a range of engineering and manufacturing skills to produce correctly, but were not themselves a critical mechanical component.
In the original whistle shown here, pressurized steam comes out from within the bottom cup and exits through the thin gap (barely visible in the image, it’s very narrow) between the cup and the flat shelf-like section of the central column. That ring-shaped column of air is split by the lip of the bell above it, and the sound is created. When it comes to getting the right performance, everything matters. The pressure of the air, the size of the gap, the sharpness of the bell’s lip, the spacing between the bell and the cup, and the shape of the bell itself all play a role. As a result, while the basic design and operation of the whistles were well-understood, there was a lot of work to be done to reproduce whistles that not only operated reliably in all types of weather using compressed air instead of steam, but did so while still producing an authentic re-creation of the original sound. As [Steve] points out, “with any project that’s not been done before, you really can’t do too much testing.”
Embedded below is one such test. It’s slow-motion footage of what happens when the whistle fires after filling with rainwater. You may want to turn your speakers down for this one: locomotive whistles really were not known for their lack of volume.
Whistle consists of 16 steam engine whistles around Newcastle. From June 22 to September 9, you can hear the whistles at 1pm. First one whistle sounds, then another, then another after that. In all, 16 whistles are included in the art installation, all controlled by Raspberry Pi computers. The Pi’s were programmed by Nebula Labs. Tech details are slim on this one, but we’re guessing each Pi has a Cellular radio built-in.
The whistles used in this installation aren’t old train whistles. They are brand new cast brass whistles based upon the original steam train sounders. The compressed air available today doesn’t sound exactly like steam though, so the brass whistles were modified to sound more authentic. [Steve’s] idea is to get the whistle as perfect as possible, which will trigger the memories of those who are old enough to have heard the originals.
To you, the rapid pitch changes made by the little ball that’s inside a ref’s whistle sounds like “trilling” or “warbling” or something. To [Oona], it sounds like frequency-shift key (FSK) modulation. Could you make a non-random trilling, then, that would sound like a normal whistle?
Her perl script says yes. It takes the data you want to send, encodes it up as 100 baud FSK, smoothes it out, adds some noise and additional harmonics, and wraps it up in an audio file. There’s even a couple of sync bytes at the front, and then a byte for packet size. Standard pea-whistle protocol (PWP), naturally. If you listen really closely to the samples, you can tell which contains data, but it’s a really good match. Cool!
The inlaid image is a controller board which [Limpkin] developed to add whistle control as a home automation option. It has an effective range of around fifteen feet and does a good job of detecting whistles from many different people. Here is one of the test subjects (captured with a hidden camera) whistling to the white LED lamp in order to switch it on.
The board is quite small. [Limpkin] holds it up in the beginning of his test video, which gives a good sense of scale. One end has a barrel jack through which the board gets power. The other end has a two conductor screw terminal which is used for switch your devices. An N-channel MOSFET protects the circuit when a heavy external load is connected. It is capable of driving a respectable 90 watts. If you’re looking to switch mains rated devices you’ll need to bring your own relay to the party.
Audio processing is handled by the Freescale ARM Cortex M4 chip at the center of the board. The Serial Wire Debug (SWD) clock and data pins are both broken out to solder pads so the thing is hackable. [Limpkin] posted the schematic, gerbers, and a code template. But he didn’t release the algorithms he uses for processing so if you want to make this at home you’ll need to figure that out for yourself. If you need help you should check out this whistle-based remote control.
You know how to whistle don’t you? You just put your lips together and blow. But do you know how to make the electronics around you react to your whistled commands? Well [Befi] figured out a system that allows him to assign a whistled command to various home electronics.
He’s using a set of RF remote control outlets to switch power to various devices like a desk lap, or a turn table. The board you see in the image above is the remote control that came with the system, but that chip is an ATmega8 which he added to give round-about USB connectivity using a serial-to-USB converter. The technique is simple enough that we’d bet you can get this to work with an ATtiny2313 and the V-USB project but that’s another story.
The additional piece is the use of embedded Linux to detect and process whistled commands. In the video after the break [Befi] explains that he’s using a Dockstar along with a microphone to capture audio input. It uses a Fast Fourier transform algorithm to process the clip and pushes commands to the remote control after processing is complete. Continue reading “Whistle Controls For You Home Electronics”→