NASA's audio recordings of planets, particularly Saturn, have sparked curiosity and fascination among the public. The Saturn Kilometric Radiation track, in particular, has circulated widely, with its haunting, organ-like wail resonating with many. However, the popular framing of these recordings as 'sounds' of planets is almost entirely wrong in its physics. Sound requires a medium to propagate, and the interplanetary medium is too diffuse to carry pressure waves at human-audible frequencies. Instead, spacecraft like Voyager and Cassini record electromagnetic signals, which are then translated into audio for human ears. The Saturn recordings, for instance, are plasma-wave emissions captured by the Radio and Plasma Wave Science instrument aboard Cassini, which were converted into audio files by shifting and compressing the signal so that the frequency structure became audible. The rising and falling tones, the dissonant chord-like swells, and the moments where the signal seems to breathe are all real structures in the radio emission, simply translated into a format the human ear can perceive. The haunting quality of the Saturn audio is partly due to the coincidence of frequency sweeps and harmonic relationships that resemble musical pitch contours. However, the recordings are not unique acoustic fingerprints; they are one rendering among many possible renderings of an electromagnetic dataset, shaped by the team's choices about playback speed, frequency band selection, and gain. The rotation-period puzzle remains unresolved, with Cassini's radio observations giving different values for the rotation rate depending on the hemisphere. The audio files capture this complexity indirectly, with the pulsing drone reflecting the planet's rotation. In conclusion, while the recordings are real data faithfully translated, the haunting quality is a side effect of physics that happens to produce frequency structures human ears find evocative. Space remains silent in the strict acoustic sense, but the instruments are listening to a different kind of signal, and the audio files are what happens when that signal is handed to a species that evolved to hear.
