Modems Unplugged

Sound Representation

This activity involves listening to songs and finding hidden messages based on the same principle as a modem.

The binary number activity briefly mentions how text could be coded using sound — high and low beeps represent binary digits, which in turn can be decoded to numbers that represent the letters of the alphabet.

There are three sets of songs provided here. The first two zip files contain “songs” that decode to English, and a set that decode to Chinese. These songs are simpler to decode; they were recorded by a jazz singer, Susan DeJong, and pianist Michael Bell. The songs in the first file decodes to English phrases, and the second one to Chinese phrases. The songs are currently available from the following two links, although this location is likely to change soon:

“Songs” that decode to English

“Songs” that decode to Chinese

To decode the songs, transcribe a 1 for each high note, and a 0 for each low note. The notes (bits) are in groups of 5, which should be translated to a decimal number. For the English messages, 1 decodes to A, 2 to B, and so on. For Chinese, the numbers 1 to 4 represent tones 1 to 4, then 5 is A, 6 is B, and so on. For more details, see the PDF file in the box on the right.

The major challenge is in the video “Reaching out” (below, and available for download from vimeo.com/23952295), which contains over 20 hidden binary message in total. The main message can be decoded by noting the pitches of the main tune as for the previous songs (which leads to a reward for diligent students); but there are over 20 messages coded in different parts of the video, including the other instrumental parts, background images, and the dancing.

Downloads

 

Hall of fame

The names of the first few people to decode various parts of the music video will be posted here; the hidden messages in the song tell you how to get your name here!

  1. The very first correct decoding was completed by a family team effort: The Engelberg Family (Mark, Alex, Mindy and Molly) from Everett, Washington, USA. In addition to decoding the messages to get to the hall of fame, they found 7 additional hidden messages in the song. Congratulations!

Band

Videos

Related Resources

  • Phil Tulga has a musical activity coding words as morse, and then writing music with it. Morse uses the idea from information theory that more probable symbols should have shorter codes, so there’s computer science in that too!
  • The Wikipedia entry on modems provides details on how more conventional modems work: http://en.wikipedia.org/wiki/Modem
  • Bacon’s cipher uses a very similar principle, where 5-bit codes are hidden in a text, usually by changing the typography of the letters instead of using high and low notes.
  • An app called “Chirp” transmits data (such as pictures, notes and links) between phones using sounds to represent the binary code. The sounds are more complex than the ones used in this activity, but the principle is the same. There’s a video about it here.
  • Vi Hart has written music using binary numbers as the basis for the rhythm.

 

Curriculum Links

Great Principles of Computer Science
  • Communication, Recollection
ACM K12 Curriculum
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  • Level I (Grades 3-5) Topic 2: Discuss common uses of technology in daily life and the advantages and disadvantages those uses provide
  • Level I (Grades 6-8) Topic 9: Demonstrate an understanding of concepts underlying hardware, software, algorithms, and their practical applications
New Zealand Curriculum
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  • Mathematics Level 1: Number strategies