What do we mean by "sound" in space?

Pressure waves like those in the atmosphere that we normally think of as sound do not propagate at audible frequencies in the extremely low density gases that fill space. However these low density gases, typically a few to a few hundred particles per cubic centimeter, are mostly charged, so the particles can interact at a distance via electric and magnetic fields. Mix in rotating planetary and solar magnetic fields, sources and sinks of particles, ionizing radiation and other sources of energy, and an orchestra of wave modes arise. Many of these plasma waves occur naturally at audible frequencies, although a human would not be able to hear them in space because the pressure is far too low. They are associated with moving particles, so, theoretically, an ultra-sensitive microphone might be able to record some plasma waves. In practice, the oscillating electric and magnetic field components are very easy to detect with antennas, so that is what we do. These waveforms can simply be played back as audio through a speaker without any modification.

In other cases, for example auroral kilometric radiation, radio waves which propagate above the frequencies of plasma waves (with no particles involved in their propagation) are recorded and played back more slowly, shifting their high frequencies down into the range of human hearing.

For a more formal introduction to waves in space plasmas, see the tutorial article by Dr. William Kurth.

For a very accessible introduction to space audio, see "What Space Sounds Like - ACOUSTICS" from The Point Studios on YouTube. (And while we're on the topic, note that there are a huge number of fake space sound videos on YouTube. Beware! The planets don't actually emit meditation music.)

Oh, and be sure to explore all of the examples below!

Start with these.

Voyager 1 PWS first interstellar audio recordings
Ongoing observations of shock-associated waves

Selected Sounds of Space
A sampling of Don Gurnett's favorite sounds of space

Van Allen Probes EMFISIS Waves or EMFISIS MAG audio samples
Audio clips from the twin Van Allen Probes

Juno Waves audio samples
Starting with Juno crossing Jupiter's bow shock

If sound bites aren't enough, try these longer selections.

Voyager-1: Jupiter Encounter
The complete day Voyager 1 spent at Jupiter

Voyager-2: Arrival at Jupiter
The clash of the solar wind with Jupiter's immense magnetosphere

Voyager-1: Saturn Encounter
Saturn encounter, November 12-13, 1980

Voyager-2: Saturn Encounter
The entire Saturn encounter from August 24 to September 7, 1981

Voyager-2: Uranus Encounter
Uranus flyby from January 23 to 29, 1986

Voyager-2: Neptune Encounter
Neptune flyby from August 23 to 25, 1989

Here's a collection of older features.

Cassini Listens to Lightning at Saturn
The crackle and pop of lightning deep in the planet's atmosphere

Cassini Observes Saturn Kilometric Radiation
The eerie sounds and bizarre features of Saturn's radio emissions

Voyager Termination Shock
Plasma wave sounds at the solar wind termination shock

Cassini Encounters Saturn's Bow Shock
Where the solar wind collides with Saturn's magnetic field

Radio Rotation of Saturn from Cassini RPWS Measurements
The puzzling change in Saturn's radio rotation period

Sounds of Space and the Kronos Quartet "Sun Rings"
The pre-performance presentation

Terry Riley's "Sun Rings" performed by the Kronos Quartet
The musical production inspired by sounds of space

Heliospheric Radio Emissions Detected by Voyager
Audio from the edge of the solar system

Type III Radio Bursts from the Oct 28 and Nov 4, 2003, Solar Flares
The signatures of record-setting solar eruptions

Sounds of the Magnetosphere
Sounds collected by the Polar spacecraft

Sounds of Space
General information

These are our related research projects.

UIowa Radio and Plasma Wave Group

Juno Waves Investigation

Van Allen Probes EMFISIS Waves Investigation

Cassini Radio and Plasma Wave Science

Cluster Wideband (WBD) Plasma Wave Investigation

Voyager Plasma Wave Spectrometer

More sources of space audio public outreach . . .

View Space Audio videos on YouTube.

@SpaceAudio in the Fediverse!