electromagnetic wave

Thread Starter

Lightfire

Joined Oct 5, 2010
690
ok voice is transmitted thorugh em wave but how? does the em wave carry it? :
and receiver gets the em wave and convert it to its original for m...
 

vpoko

Joined Jan 5, 2012
267
I'm not 100% sure I understand what you're asking, but I'll take a stab at it. When transmitting voice over EM waves, the voice is modulated over a carrier wave. For AM, you start with a sinusoidal carrier wave of some set frequency. Then you make changes to that carrier wave depending on the signal - in areas where there's more signal, the amplitude of the carrier wave is increased above where it would be had the signal not been modulated over it. For FM, the process is similar, except the signal impacts the frequency of the carrier wave instead of its amplitude.

This picture shows an AM example: http://img.tfd.com/cde/_AMMOD.GIF
While this pictures shows an FM example: http://img.tfd.com/cde/_FMMOD.GIF
 

Wendy

Joined Mar 24, 2008
23,415
The phrase you are looking for is modulation. There are many forms of modulation.

When referring to radio frequency RF is the better choice of initials to em. Light is em, so are gamma rays, and lasers. The electromagnetic spectrum is vast, we use a small part of it.
 

Thread Starter

Lightfire

Joined Oct 5, 2010
690
meaning the sound is in modulation??????

Sorry guys for my sentence..

I really dont know how electromagnetic or RF wave extract the sound...

so meaning,,, everys ingle modulation would result to different sound?? ah??
 

vpoko

Joined Jan 5, 2012
267
Demodulating would recover the original signal, be it a sound or something else. If you ignore transmitting sound over radio waves (or any kind of EM waves since you could modulate light waves, etc) and just think of sound as pressure waves in a medium, it's the details (frequencies, amplitude, harmonics, phase, etc) of those pressure waves that determine the sounds you hear. Modulation "encodes" that already-existing signal onto another wave.
 
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