ep-413 DSP – week 14

Earth, air, fire, and water

Waves that are not sound waves.


Transmitting music with light

light: https://reactivemusic.net/?p=8487

Analog radio/TV transmitters

A simple Arduino AM transmitter (Morse code) https://reactivemusic.net/?p=4450 (antenna pin D8) on 1.337 MHz

Raspberry Pi-rate radio. FM stereo transmitter using R-Pi and a piece of wire: http://makezine.com/projects/make-38-cameras-and-av/raspberry-pirate-radio/ Also see: https://reactivemusic.net/?p=10186

Analog TV transmitters, using RF Modulators and Old VCR’s: https://reactivemusic.net/?p=12355

Software defined Radio (SDR)

using Max and Pd

rtl-sdr – inexpensive open source software defined radio

Software defined radio in Max http://zerokidz.com/radio (The user guide http://zerokidz.com/radio/docs/maxsdr5.pdf and tutorials provide a basic introduction to working with radio signals in the audio domain.

Transmitting sound in water

Transmitting signals in water https://reactivemusic.net/?p=853

Internet radio streams and recordings


  • What is the difference between sound waves and radio waves?
  • What is an antenna?
  • Wave propagation is frequency dependent
  • Sunspots and magnetic fields http://spaceweather.com
  • Extreme frequencies, negative frequencies?

The speed of sound is 340 m/s in air (1497 m/s in water)

Speed of light is 300,000,000 m/s

wavelength = velocity / frequency

“I think [radio] is just the biggest conceptual art project uninentional or otherwise that anyone ever made. it puts Christo and those other guys to shame. Its planetary”

Roman Mars “Episode 97 – Numbers Stations” from 99% Invisible

Frequencies and modes

  • Macbook trackpad: Noise 5 mHz. (try holding radio near screen too)
  • Macbook AC adapter: Noise 600-1400 kHz. (~1000)
  • AC adapters, LED’s, Utility poles: 3.2 Khz
  • Arduino transmitter: AM 1330 kHz.
  • Laser light at 650nM
  • Wireless micorophone (Orange-brown): Wide FM 614.150 MHz. (R band)
  • Cordless phone: Narrow FM 926 mHz.
  • Cell phone: Digitally encrypted trunking FM 836 mHz.
  • Wifi: Digitally encoded PCM 2.4 gHz.
  • FM broadcast band: Wide FM 89.7 mHz (Raspberry Pi example 98.1 Mhz)
  • TV audio 600 mhz/660 mhz FMW
  • The sun http://www.ips.gov.au/Solar/3/4

Looking for more…

This blog has many stories about experiments waves. Try searching, for example, for: “radio” https://reactivemusic.net/?s=radio


Please send me copies of your earlier compositions. [email protected]

  • the future
  • a sound byte
  • internet API data (extra credit)
  • magical fx

Note: if you played the music in class but lost the recording, Max patch – or if it was a live performance – just let me know, in case I have forgotten. Thanks.

Here is a description of the composition for next week:

Write a composition to induce magical effects.

Here is an example from Aseem Suri http://www.aseemsuri.com/journal/piece-of-mind-second-run-at-the-csound-conference

The project was derived from computer technology, but the overall effect was that people would go into a mysterious room, for a minute, and when they emerged, they would be smiling and happy.

Due on December 15th (last class)