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Space acoustics

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Tue, 2012-04-03 11:30

Arenamontanus Arenamontanus's picture

Space acoustics

While vacuum doesn't transmit sound at all, what about the planetary atmospheres of EP? Here is a short radio interview with some researchers who simulated the acoustic effects on Venus and Mars: http://www.pri.org/theworld/?q=node/22451 http://www.southampton.ac.uk/mediacentre/news/2012/apr/12_59.shtml For those who want the science (and have academic access), the papers are Leighton, Timothy G. and Petculescu, Andi (2009) The sound of music and voices in space part 1: theory. Acoustics Today, 5, (3), 17-26. http://eprints.soton.ac.uk/71546/ Leighton, Timothy G. and Petculescu, Andi (2009) The sound of music and voices in space part 2: modelling and simulation. Acoustics Today, 5, (3), 27-29. http://eprints.soton.ac.uk/71545/ Some notable passages:

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Under this assumption, Bach’s Toccata and Fugue in D minor (293.66 Hz) played on Titan will automatically be transposed down to the key of ~F# minor (185 Hz). The atmospheres of Mars (Fig. 3) and Venus (Fig. 4) are both dominated by CO2 and N2. However, their surface temperatures are extremely different, leading to ground-level sound speeds that are, respectively, 70% and 120% of the sound speed on Earth.52 Thus Mars’ thin and cold (-46 oC) atmosphere transposes Bach’s Toccata down to ~G# minor (207.65 Hz), while Venus’ dense and hot (457 oC) atmosphere transposes it up to ~F minor (349.23 Hz)—nearly an octave above Titan’s rendition at F# (185 Hz).

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The acoustic absorption, on the other hand, affects the propagation of sound in a different manner on the four worlds. Thus Titan’s nitrogen-based atmosphere is less lossy than Earth’s, so that the music can carry to similar distances (although, as on Earth, variations due to season and latitude, atmospheric stratification and any wind could become important, especially at very long distance propagation e.g., of infrasound). The CO2 on Mars and Venus absorbs the sound far more than does Earth’s air, such that on Mars the music at full volume is barely audible merely 10 meters from the organ

This is obviously game relevant on Mars - sound stealth is much easier, even with a bit of terraformed atmosphere.

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The fact that Venus has the opposite effect with flue and reed pipes on the same instrument shows that the effect of an alien world on the sound generated by a given musical instrument therefore depends on the details of the mechanism by which that sound is generated.

For those who really want to nerd out, see Leighton, T. G. (2012) The use of extra-terrestrial oceans to test ocean acoustics students. [in special issue: Part 2 Education in Acoustics] The Journal of the Acoustical Society of America, 131, (3), 2551-2555. for dealing with alien oceanic acoustics and the paper Atmospheric acoustics of Titan, Mars, Venus, and Earth by Andi Petculescu and Richard M. Lueptow http://www.peppermintleafresearch.net/Andi/paper_icarus.pdf for some other analysis. The main conclusion seems to be: exoplanets will tend to sound odd. Worlds with thin atmospheres will be silent and noise dampened, while worlds with dense atmospheres could carry sound well - but it depends on the composition. Density and composition shifts tones up and down, but some instruments or objects change timbre in odd ways.

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Tue, 2012-04-03 13:24

Ashen Victor Ashen Victor's picture

Re: Space acoustics

Amazing article! Thanks arenamontanus! This is very useful, not only concerning stealth and verbal comunications, but it gives some sweet ideas to add colour and taste (pardon the pun) to our games. I suppose people accustomed to roam the martian countryside screams rather than talks when they return to a pressurized habitat: -HELLO EVERYBODY! IT´S BEING SIX MOOOONTHS! HOW IS LITTLE TIMMY? -Shut up you redneck!

Wed, 2012-04-04 12:14

Prophet710 Prophet710's picture

Re: Space acoustics

Any soundbites?

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"And yet, across the gulf of space, minds immeasurably superior to ours regarded this Earth with envious eyes. And slowly, and surely, they drew their plans against us."

Fri, 2012-04-13 15:26

nerdnumber1 nerdnumber1's picture

Re: Space acoustics

This is quite interesting, but there are some other factors that need to be taken into account. Firstly, most worlds that you will be listening on are at least partially teraformed (like Mars and upper-atmosphere Venus) bringing them somewhat closer to Earth norm. Secondly, while sound drops off quickly on Mars, so would background noise. Furthermore, the dropoff is related to distance, so if you're standing next to someone, it really wouldn't be that different from Earth, meaning that Martians would be used to using normal tones at close distances at least (also, while distance penalties on hearing perception might accrue faster, close range hearing should be fine). Lastly, there are probably a few common mesh programs that fix the worst of the distortion if it turns out to be a big problem. It makes for nice flavor, but shouldn't be too hindering in game terms. Transhumans can jump between Luna and Venus without much penalty for the gravity, so I think they can adjust to the acoustics just fine.

Sat, 2012-04-14 09:05

Arenamontanus Arenamontanus's picture

Re: Space acoustics

nerdnumber1 wrote:
This is quite interesting, but there are some other factors that need to be taken into account. Firstly, most worlds that you will be listening on are at least partially teraformed (like Mars and upper-atmosphere Venus) bringing them somewhat closer to Earth norm.

A bit, but not much. Remember that the Martian air pressure still is quite low. And the Venusian upper atmosphere might have roughly Earth pressure and temperature, but is mostly carbon dioxide - it is pretty dense (hence the aerostat cities).

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Secondly, while sound drops off quickly on Mars, so would background noise. Furthermore, the dropoff is related to distance, so if you're standing next to someone, it really wouldn't be that different from Earth, meaning that Martians would be used to using normal tones at close distances at least (also, while distance penalties on hearing perception might accrue faster, close range hearing should be fine).

What limits what we can hear is the signal-to-noise ratio and the sound amplitude. With fast decay the SNR for nearby conversation would indeed become better, but you would still need to speak louder even over fairly short distances.

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Lastly, there are probably a few common mesh programs that fix the worst of the distortion if it turns out to be a big problem.

Which of course suggests that auditory processing might be a popular app for other reasons too. Why not give your boss a squeaky voice? Or translate him? Or add proper background music while compensating for noise?

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It makes for nice flavor, but shouldn't be too hindering in game terms. Transhumans can jump between Luna and Venus without much penalty for the gravity, so I think they can adjust to the acoustics just fine.

I rarely care about the game terms. I care much more for being able to describe the wonder and alienness of the environment.

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Mon, 2012-04-16 15:59

nerdnumber1 nerdnumber1's picture

Re: Space acoustics

Quote:
Which of course suggests that auditory processing might be a popular app for other reasons too. Why not give your boss a squeaky voice? Or translate him? Or add proper background music while compensating for noise?

Real-time translation and entopic skins that add background music and similar effects are explicitly described in the core rulebook.

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I rarely care about the game terms. I care much more for being able to describe the wonder and alienness of the environment.

Many characters/players I've seen have a keen eye for any advantage that they can exploit. "I can appreciate the unique alieness of the environment, but tend to be more interested in how it will affect my survival chances." Dark and stormy night just means that it is easier to sneak up and slit your throat :P

Thu, 2012-04-19 02:59

Aeroz

Re: Space acoustics

Just my two cents, but I question a transhumans ability to hear. They no doubt do, but being able to hear something and registering sound are not the same thing. Hearing is a skill you must keep practicing for your mind to connect what you are hearing with some intent. But with AR and wireless communication, how often do people really use soundwaves to hear? They'd probably be used to audio files far more, and as such they are used to perceiving sound at what humans would consider normal. Which would probably mean actual sounds are alien. I imagine it would be similar to hearing something while underwater. If you put in the effort you can probably figure it out, but otherwise its all gibberish.

Thu, 2012-04-19 04:34

Arenamontanus Arenamontanus's picture

Re: Space acoustics

Good point. Divers apparently need to learn how to interpret the sounds in high pressure environments (especially with helium atmospheres) in order to make sense of them and understand what is being said.

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