Pea-Whistle Steganography

Do you see the patterns everywhere around you? No? Look closer. Still no? Look again. OK, maybe there’s nothing there.

[Oona Räisänen] hears signals and then takes them apart. And even when there’s nothing there, she’s thinking “what if they were?” Case in point: could one hypothetically transmit coded information in the trilling of a referee’s whistle at the start of a soccer match?

acme-spektriTo 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!

[Oona] has graced our pages before, naturally. From this beautiful infographic tracing out a dial-up modem handshake to her work reversing her local bus stop information signs or decoding this strange sound emitted by a news helicopter, She’s full of curiosity and good ideas — a hacker’s hacker. Her talk on the bus stop work is inspirational.. She’s one of our secret heroes!

Just put your lips together to turn on a lamp


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.

Whistle controls for you home electronics

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”

Lunkenheimer steam whistle, doorbell

We’re going to straight out agree with [Pete] on how surprisingly quiet doorbells are now a days, and if we had it our way we would put his Lunkenheimer train whistle doorbell in every home*. The setup he uses is surprisingly simple, opting for a pre-built wireless doorbell that signals a microcontroller which in turn drives a relay and solenoid. While he does include a video, we felt it didn’t quite show the intensity of these whistles.

*HaD is not responsible for hearing loss and subsequent melted brains.