Ground control to Major Tom
Your circuit’s dead, there’s something wrong
– ‘Space Oddity’, David Bowie
[Beep] [Static] … [Beep] [Static] … [Beep] [Static] … Houston, we have a cliché … [Beep] [Static]
Yes, Action Science Theatre has gone into orbit, and how better to evoke the golden era of space exploration than with some beepy, staticky conversation? Now, I know that we’re no longer in the golden age of space exploration, and that Commander Hadfield’s broadcasts from the ISS had nary a beep nor a burst of static to be heard, but blah blah mindvisible images and so on.
So, firstly the beeps. During the Apollo space missions, NASA communications relied on beeps called Qunidar Tones. These were used to switch on and off the remote transmitters across the world that were used to track and communicate with the space vehicles. They can be clearly heard in a recording made during the Apollo 11 mission that is posted on sound effects blog The Sound and the Foley.
Recreating Qunidar tones is very easy, thanks to the the Tone Generator in audio-editing software Audacity. Simply set the waveform to sine wave, the frequency to 2525 or 2475 Hz (I went for the 2525 ‘opening’ tone for the podcast) and the duration to 250 ms, and bingo. Or beepo.
So what about the static? Digging through Audacity’s ‘Generate’ menu reveals an option called ‘Noise…’. On clicking this we are presented with three choices: white, pink and brown.
Pink noise? Brown noise?
Let’s start with the one everyone has at least heard of. The term ‘white noise’ has entered general use to mean any form of random, unintelligible background noise. There is even a horror film of the same name. Strictly speaking, however, white noise is a very specific form of noise in which the intensity of the signal is the same at all frequencies within a given frequency band.* In human terms, though, what you hear is simply a hissing noise. The name was given by analogy with white light, which has a similar spectrum (i.e. pure white light is produced when the intensity of each individual wavelength [colour] is the same).
Pink noise is a variant of white noise in which the signal is adjusted so that the energy in the signal is equal at each octave. The result – for reasons that are explained quite well in a post at techtarget.com – is that pink noise (named because light with this type of spectrum is pink) sounds slightly lower in pitch than white noise to the human ear. Unlike white noise, pink noise spectra occur naturally, arising in, for example, weather patterns, starlight, and electronic devices. Pink noise also occurs as the background static during communications in podcasts about the ISS…
The principle of generating small amounts of finite improbability by simply hooking the logic circuits of a Bambleweeny 57 Sub-meson Brain to an atomic vector plotter suspended in a strong brownian motion producer (say a nice hot cup of tea) was, of course, well understood
The Hitchhiker’s Guide to the Galaxy – Douglas Adams
Brown (or Brownian) noise is named, not after brown light, but after Robert Brown. Brown discovered the phenomenon of Brownian motion, in which particles suspended in a liquid appear to jiggle about randomly as a result of being bombarded by the molecules in said liquid, and brown noise is the noise produced during the process. Brown noise is similar to pink noise, but with a greater reduction in intensites at higher frequencies, sounding lower still than white or pink noise to the human ear.
So there you have it. You don’t have to be a synaesthete to listen to coloured sound.
*I did try look all this up on Wikitextbook, but it just made my eyes bleed.