Re: OT: sound speed depends on frequency on mars

On 31/08/2024 3:10 am, john larkin wrote:

On Sat, 31 Aug 2024 01:23:19 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
 

On 31/08/2024 12:34 am, john larkin wrote:

On Fri, 30 Aug 2024 11:13:05 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
>

NASA's Mars rover Perseverance has found that sound travels much more slowly on the Red Planet than it does on Earth
and behaves in some unexpected ways that could have strange consequences for communication on the planet.
https://www.space.com/nasa-mars-rover-perseverance-speed-of-sound#main
   At frequencies above 240 Hertz, "the collision-activated vibrational modes of carbon dioxide molecules do not have enough time to relax, or return to their original state,"
   the researchers said, which results in sound waves at higher frequencies traveling more than 32 feet per second (10 m/s) faster than the low-frequency ones.
   That means that if you were standing on Mars, listening to distant music, you would hear higher-pitched sounds before you would hear the lower-pitched ones.
>
paper:
https://www.hou.usra.edu/meetings/lpsc2022/pdf/1357.pdf
>
So...
Music from far away may sound funny?
>
For Mars we will need compensation headphones with distance measurement and variable delays....
;-)
>
Better use radio.. and earplugs/ headphones...

>
Funny, I just delivered a lecture on transmission lines and noted that
microstrips have dispersion from  the unbalanced dielectric constants
and skin effect. Rising edges get sloppy at the and of a long trace.

>
I hope you pointed out that buried strip-line isn't dispersive. I have
pointed this out here from time to time.

 Of course it's dispersive, maybe a bit less than microstrip.

Why do you think that?

It's hard to keep up decent impedances on stripline in a multilayer
board, especially 8 or 10 layers.

Stripline is buried between two ground planes. The only tricky part of impedance control is the thickness of the dielectric in the two layers above and below the strip-line. In a ten layer board this is thinner than it would be in a board with fewer layers.
Pay enough for close-tolerance substrates in the two relevant layers and you should be okay.

https://www.wevolver.com/article/stripline-vs-microstrip

 >>

I wonder if anyone has added surface-mount Heaviside loading coils to
a PCB trace.
>
https://en.wikipedia.org/wiki/Loading_coil

>
It would be a bit silly.

 Most ideas seem silly to people who are by nature hostile to ideas.

Not a problem I've got.

Dismissing is easier than thinking.

Thinking about what a loading coil might be doing to the impedance of a PCB trace isn't something that you seem to have managed to do.
--
Bill Sloman, Sydney