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Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Bill Sloman <bill.sloman@ieee.org> Newsgroups: sci.electronics.design Subject: Re: OT: sound speed depends on frequency on mars Date: Sat, 31 Aug 2024 16:17:39 +1000 Organization: A noiseless patient Spider Lines: 70 Message-ID: <vaucih$th84$1@dont-email.me> References: <vas9g2$1so9m$1@solani.org> <vgl3dj9uq2t9bmo6miqr8faaiuoi1d24c2@4ax.com> <vaso5i$hnfl$1@dont-email.me> <2uu3djptvil2j5vberhsj4otm3nbd6l557@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Sat, 31 Aug 2024 08:17:54 +0200 (CEST) Injection-Info: dont-email.me; posting-host="689e4fbc7162e6b65303ac32e4b590ab"; logging-data="967940"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19nn0ubTFC3kJaU6WAhKbxLQwbI7EJ3i68=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:3VWRWWi1geQjw2Tfahiekdjkp3s= In-Reply-To: <2uu3djptvil2j5vberhsj4otm3nbd6l557@4ax.com> Content-Language: en-US X-Antivirus: Norton (VPS 240830-4, 30/8/2024), Outbound message X-Antivirus-Status: Clean Bytes: 4133 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