The description from the Uranis video says:
"On the 24 January 1986, the probe Voyager 2 passes through the Uranus system.
The probe is carrying different detectors : magnetometers, plasma detectors, low-energy charged particles detectors, cosmic rays detectors, radiowaves receivers.
Recordings were made.
Interractions of the solar wind with planet's magnetosphere, magnetosphere itself, electromagnetic fields, charged particles emissions, charged particle interactions of the planet, its moons, and the solar wind.
All this electromagnetic phenomenons can be transformed into electric signals, which can in turn be amplified and used to excite the membrane of a loud speaker ; thus making audible to the human ear the rustling of the cosmos.
All these sounds were recorded while Voyager 2 was passing by Uranus, and assembled without manipulation.
From "Symphonies of the Planets vol.9 - Uranus" Nasa Voyager Recordings, Brain/Mind Research, 1990."
So the sounds are probably converted from several different sources, maybe even different ones from the different planets... It also makes sense to me since the sound from some of the planets seemed to change completely in structure sometimes (at least Saturn).