3
$\begingroup$

Background:

I was looking at a lot of the voyager spectrograms and listening to their sounds and I was honestly starting to wonder whether or not they had any sort of ambient noise negation applied to them. Usually when a film crew wants to film in a room, they take a bit of "ambient room noise" recording for each of the rooms and surroundings, then use these to make the audio crisp and clear for viewers. By recording this ambient noise, they are basically stripping all white noise from the background and getting crisp audio of something, such as a person speaking (or even to add noise back in to match if they need to rerecord audio).

If you look at this example spectrogram, you can actually see noise patterns (that are not random) which is usually the result of some mechanical ambient process. I'm guessing some of the mechanical noise from the probe could also be removed. A good example of a repeated pattern I think is coming from the probe would be:

that 7 band beep of increasing density, this is an example of the ambient mechanical noise I was intending to describe, same with the constant 2.3kHz uniform band.

Spectrogram of Jupiter flyby

I was wondering if Voyager 1 or 2 actually implemented any of these methodologies (I'm assuming no because you can hear beeping, machines whirring, parts moving, etc). It would be cool to get the ambient mechanical noise recordings from its time in a vacuum and use these to isolate the real sounds of the planets without the sounds of the probe itself.

The main question:

  • Did voyager also record in the vacuum and send data back to Earth?

  • Did any of this data get publicly published?

$\endgroup$
  • $\begingroup$ If there are public recordings, I suspect they would include the original raw data without any noise cleanup - having raw data is vital to making corrections if a processing error is discovered later. If you find such recordings, you could do some analysis on 'silent' segments and then run an appropriate filter over the entire set. $\endgroup$ – brichins Sep 5 '18 at 20:27
  • $\begingroup$ @brichins you're not wrong there, the ones posted for the fly-bys are unedited. $\endgroup$ – Magic Octopus Urn Sep 5 '18 at 20:49
  • $\begingroup$ White noise is random. If you can actually see noise patterns (that are not random), it is no white noise. "stripping all white noise from the background" is not possible, because white noise is not predictable, it is random. $\endgroup$ – Uwe Sep 6 '18 at 15:56
  • $\begingroup$ @Uwe I mixxed terms a lot, I was talking about ambient mechanical noises. $\endgroup$ – Magic Octopus Urn Sep 6 '18 at 16:07
  • $\begingroup$ @Uwe a good example of a repeated pattern I think is coming from the probe would be: youtu.be/w80jOLHgdHE?t=289 that 7 band beep of increasing density, this is an example of the ambient mechanical noise I was intending to describe, same with the constant 2.3kHz uniform band. I've updated that example too. $\endgroup$ – Magic Octopus Urn Sep 6 '18 at 19:12
7
$\begingroup$

I think you might have some misconceptions about what that spectrogram represents, and how it might have been processed.

The purpose of recording audio "room tone" is not to remove background noise, but to add it back in during post processing, to make sound edits less jarring. It would be useless for removal of true, uncorrelated noise.

The spectrogram you're looking at covers audio frequencies, but it's actually depicting data from an instrument that measures electromagnetic waves, not sound, so any noise components would not be of mechanical origin. The PWS instrument measures the frequency spectrum directly; it is calibrated by injecting known signals (prior to launch) and measuring the resulting outputs, rather than by subtracting out some sort of baseline "quiet" signal.

It's possible that some components of the spacecraft emit electromagnetic signals during operation (for example, hardware clock signals or other repetitive/cycling processes) at some cadence that falls into the sensitivity range of the PWS instrument. The engineers would have tried to minimize these effects when designing the probe, but completely mitigating all possible sources of electromagnetic interference is rather difficult. Scientists analyzing the data would most likely need to refer to detailed calibration and performance reports from the instrument engineering team, and perhaps housekeeping data from the probe itself, in order to properly interpret the data and know which features are noise, and which features are truly present in the environment.

$\endgroup$
  • $\begingroup$ Also, any idea on what a signal like this would be if it isn't the probe? youtu.be/w80jOLHgdHE?t=289 (this is the original video) It seems to be 100% artificial (many specific bands and consistently rising density). Was my main thinking behind some of the sounds being interference from the probe itself. The constant green line at 2.3kHz was also a seemingly artificial signal. $\endgroup$ – Magic Octopus Urn Sep 5 '18 at 20:36
  • $\begingroup$ Okay, yeah... I'm now seeing that a lot of these units are extremely different than the topics I studied in school (being decibels). I'll have to do more research on how the PWS scanners actually worked on voyager to get a better grasp on the true differences between audio and electromagnetic wave scanning. Do you have any good introductory articles into EM wave scanners or maybe some laymans documentation on the PWS scanner used for Voyager? (Mores in depth than the one linked)? $\endgroup$ – Magic Octopus Urn Sep 5 '18 at 20:48

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.