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Natural Science Forum / Physics / General Physics / March 2007Highest Acoustic Atmospheric Frequency?
Hello: What is the highest-frequency of ultrasound that can propagate through air on earth's atmosphere? Thanks in advance, Radium > What is the highest-frequency of ultrasound that can propagate through > air on earth's atmosphere? What makes you think there is a limit? > What makes you think there is a limit? Huh? There is no limit? So a ultrasonic sound wave with a frequency of 10-to-the- power-1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 cycles [THATS A *LOT* OF CYCLES] every 10-to-the-power-NEGATIVE -1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 of a second can travel through air on Earth's atmosphere???????!!!!!!!!!!!!?!?!?!?!?!?!?! If not, then what stopping it from???????!!!!!!?!?!?!?!?!?!?!?!?! You said there is no limit!! Sorry for my loudness, I just extremely frustrated over a question that I can't answer. Its like trying to solve an impossible math problem. Please don't be offended. 10^-1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 second = 10-to-the-power- NEGATIVE-1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 of a second = AN EXTREMELY SHORT TIME 10^1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 cycles = 10-to-the- power-1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 cycles = AN EXTREMELY LARGE AMOUNT OF CYCLES >> What makes you think there is a limit? > > Huh? There is no limit? There are practical limits such as sound generation, attenuation, etc. But as long as the sound wavelength is >> than the size of the medium constituents of it is propagating through... http://www.ndt-ed.org/EducationResources/CommunityCollege/Ultrasonics/cc_ut_index.htm http://scienceworld.wolfram.com/physics/topics/Acoustics.html In sci.physics, Sam Wormley <swormley1@mchsi.com> wrote on Sat, 31 Mar 2007 18:27:55 GMT <LKxPh.19946$oV.16203@attbi_s21>: >>> What makes you think there is a limit? >> [quoted text clipped - 6 lines] > http://www.ndt-ed.org/EducationResources/CommunityCollege/Ultrasonics/cc_ut_index.htm > http://scienceworld.wolfram.com/physics/topics/Acoustics.html This would make for a practical limit of about 10^-10 m (the size of an atom). Since sound speed is about 331.4 m/s at 0 degrees Celsius, the maximum frequency would therefore be on the order of 3.314 teraHertz. I'd have to look regarding intermolecular distance, which would give another, lower, limit.  Signature#191, ewill3@earthlink.net Useless C++ Programming Idea #10239993: char * f(char *p) {char *q = malloc(strlen(p)); strcpy(q,p); return q; } -- Posted via a free Usenet account from http://www.teranews.com > In sci.physics, Sam Wormley > <swormley1@mchsi.com> [quoted text clipped - 18 lines] > I'd have to look regarding intermolecular distance, which would give > another, lower, limit. About a factor of a thousand lower. :-) In sci.physics, Sam Wormley <swormley1@mchsi.com> wrote on Sat, 31 Mar 2007 19:04:37 GMT <9hyPh.20046$oV.5644@attbi_s21>: >> In sci.physics, Sam Wormley >> <swormley1@mchsi.com> [quoted text clipped - 21 lines] > About a factor of a thousand lower. > :-) Wouldn't surprise me. A cubic meter of air is about 41 moles. That same cubic meter of air, liquefied, would occupy about 1.2 liters or 1.2 * 10^-3 m^3. (Maybe not quite that, as I'm assuming the same density as water.) This suggests that the molecule-to-molecule distance might be about 10 molecules in width, for a maximum frequency of 331 GHz. Give or take. Of course this shouldn't be that difficult to measure directly. Computers routinely generate signals of more than 3 GHz (if one has a modern processor) and the overtones shouldn't be too hard to filter out and drive something along the lines of a speaker coil. So color me slightly curious. :-) Signature#191, ewill3@earthlink.net "Your mother was a hamster and your father smelt of elderberries!" - Monty Python and the Holy Grail -- Posted via a free Usenet account from http://www.teranews.com >> What makes you think there is a limit? > > Huh? There is no limit? What is the highest-frequency sound that can exist in Earth'satmosphere? http://www.lns.cornell.edu/spr/2006-11/msg0075905.html Igor wrote: The mean free path in air at sea level is about 0.1 micron[1]. Let's take the speed of sound to be roughly 300 m/s. Then the upper limit on sustainable sound frequencies is f_max = (300 m/s) / (10^-7 m) = 3*10^9 Hz = 3 GHz. > Igor wrote: > The mean free path in air at sea level is about 0.1 micron[1]. Let's > take the speed of sound to be roughly 300 m/s. Then the upper limit on > sustainable sound frequencies is > > f_max = (300 m/s) / (10^-7 m) = 3*10^9 Hz = 3 GHz. Thanks. > > Igor wrote: > > The mean free path in air at sea level is about 0.1 micron[1]. Let's [quoted text clipped - 4 lines] > > Thanks. Interesting. Sound in say seawater would have a correspondingly higher limit then. OTOH dissipative effects would show up rather sooner. I'm also reminded of an old SciAm article on generating ultrasound by sticking a hunk of quartz in a cavity resonator as a transducer; the mentioned frequency was a couple "kilomegacycles". Now I know why that quietly died away. ;>) Mark L. Fergerson > What is the highest-frequency sound that can exist in Earth'satmosphere? > http://www.lns.cornell.edu/spr/2006-11/msg0075905.html [quoted text clipped - 5 lines] > > f_max = (300 m/s) / (10^-7 m) = 3*10^9 Hz = 3 GHz. Sorry to bug you with another question. Is the "10^-7 m" part because the mean free path in air at sea level is about 0.1 micron? |
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