Sign in to follow this  
Followers 0

Radio vs Audio frequency

6 posts in this topic

Posted

Funny I just started diving into HAM stuff and for the first time realized that audio and radio were not technically on the same spectrum. I always remember those spectrum line images with light up to cosmic rays at one end and sound near the other, but after realizing radio freq's have a much longer wavelength but the frequency is technically higher really messed me up for awhile.

 

Now that I understand that radio is a propagation in relation to light and not in an air medium in regards to frequency, what is the highest audio type frequency that can be reproduced? I know we can't hear above 20k, but what is the highest frequency a human can reproduce by moving air pressure? I'm shooting in the dark of course and may have this idea completely wrong, but no doubt it is interesting.

 

I sort of answered my own question by searching a physics forum, although I no doubt for the most part don't exactly know what they are talking about. One guy suggested that it is possible for lightining to exhibit an air pressure sound pulse of upward of higher than the Gigahertz range of air pressue. Would be cool if this could in any case be recorded and lowered to be heard by the human ear haha.

 

http://www.physicsforums.com/archive/index.php/t-144509.html

Share this post


Link to post
Share on other sites

Posted

yep audio is mechanical energy, radio waves are electromagnetic energy. two different spectrums. i see audio "experts" confuse the two all the time.

 

can't tell you the highest audio frequency possible (if there is a limit), but this will throw you for a loop: a sufficiently loud enough sound in the right conditions can generate light!

Share this post


Link to post
Share on other sites

Posted

Well, maybe ask a bat, or at least observe it... although, there are probably lots of ultrasonic measuring tools around. By human, do you mean, a human larynx or rather human technology? And by frequency, do you mean a single "tone"? I'd guess, ground noise will pretty much go on the higher you go, but after a while, it will decrease, since molecules would need to change speed very rapidly while under inertia. I'd say, light and sound differ not only in different spectra but in different media. Sound needs physical material to transport the wave, be it air, water, earth or whatever. (however, I am not sure, if there is sound within a very stiff material, e.g. some crystal). Light needs a transparent material site, glass, air, a diamond or even a vacuum. Light (and electromagnetic "waves" generally) however, is way more complex to define (and I did not understand it so far). What I recover, deep down from my physics classes at high school: there are "photons" traveling on a more or less a straight path, but are distracted all the time, so that measurable results of it follow wave behavior.

Share this post


Link to post
Share on other sites

Posted

I'm certainly not a physicist but guessing the only frequency limitation on creating acoustic waves would be

the mechanical construction of  a device to generate and receive them.

 

K7XD

Share this post


Link to post
Share on other sites

Posted

Photons are electromagnetic energy that can travel in a vacuum. Phonons are vibratory waves that must propagate in a solid. They can be very high frequency. An example of high frequency sound (not necessarily phonons) that travels on a surface of quartz are SAW filters. SAW stands for Surface Acoustic Waves. We use SAW filters at 470 to 950 MHz in some receiver front ends and 70 to 254 MHz in IF filters.

Crystals used in oscillators are another example of mechanical waves in solids. The quartz bends at frequencies up several hundred MHz though usually used much lower. Any mechanical wave can be considered sound though we usually reserve it for mechanical transmission through air (sometimes water as SONAR).

Cheers,

Larry F

Lectro

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0