# Limits of information transfer through light and sound

Tags: information transfer, light, sound
 P: 2 Are there any limits for information transfer through sound or light? Or are these the limits of the devices that send and receive information through these two media. Request for clarification.
 HW Helper P: 2,155 Limits in what sense? Bandwidth, content, speed/latency?
 P: 2 Limits w.r.t bandwidth. I understand the speed limit is that of the light.
 Sci Advisor P: 5,523 Limits of information transfer through light and sound I've never thought about the bandwidth limitation of sound... I guess it's set by the viscosity of the material (the time constant of the viscoelastic response). http://www.massa.com/fundamentals.htm Shows that the signal gets rapidly attenuated about 50 kHz, but air supports acoustic frequencies well above 250 kHz.
 P: 1 If light is one of the main carriers of information along with sound, and if you look at the sun, for example, as the "main" light source, it would then seem that there is much more information coming in than can be gathered and assimilated by our current technologies we have thus far. However, if you look at solar technology and its growing ability to reflect and utilize the full solar spectrum, then the sun would be one media source and the reflector would be the other, receiving the solar information and assimilating it. Thus we are working through the limits as technology evolves.
 P: 92 I'm thinking along the lines of the speed of sound can be broken, the speed of light hasn't been broken yet, with the speed of light (optical) you are limited to the speed of light, i had a thought just before (hence replying to an old thread) using sound to transfer files wirelessly, rather then using wi-fi infared blutooth and so forth, thinking back to the first form of long range communication (morse code) then simplifying it in terms of 0's and 1's eg. sound, no sound. All that would be required is a decompiler at one end and compiler at the other end, effectivly the same as the way computers send information over the internet, only with sound instead of power. Would transfering data using sound waves (not through cables) be viable? for example, you could send a video over the radio. Thoughts?
 P: 68 If you take it to its extremes then at some point the information is going to become quantized, in a sense the intuitive world around you seems analogue but as you look closer and closer it transforms into something that is digital. I'm sure that the physical limitations on information will involve using planck's constant.
 P: 68 One clever way they use to increase the density of information in fibre optics is to simultaneously use multiple wavelengths of light, each wavelength carries different information.
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 Quote by r4z0r84 I'm thinking along the lines of the speed of sound can be broken, the speed of light hasn't been broken yet, with the speed of light (optical) you are limited to the speed of light, i had a thought just before (hence replying to an old thread) using sound to transfer files wirelessly, rather then using wi-fi infared blutooth and so forth, thinking back to the first form of long range communication (morse code) then simplifying it in terms of 0's and 1's eg. sound, no sound. All that would be required is a decompiler at one end and compiler at the other end, effectivly the same as the way computers send information over the internet, only with sound instead of power. Would transfering data using sound waves (not through cables) be viable? for example, you could send a video over the radio. Thoughts?
Radio waves do not use air as a medium. Radio waves are EM waves, just like light is.
Unfortunately the bandwidth when using sound is horribly low compared to wi-fi and most other wireless technologies. I don't know the limit for frequency in a sound wave, but I have a difficult time believing that it is in the upper MHz to GHz range, where practically all short-medium range wireless sits at.
 P: 92 Just thought of how to redesign the inter-net, thanks for all your input. Just one question, Do EM waves travel at the speed of light?
 Sci Advisor P: 2,470 What you are looking for is Shannon-Hartley theorem, which tells you how much data you can push through a certain band. This will work the same way for sound waves, light, and RF. And yes, RF propagates at the speed of light, because the only fundamental difference with light is the frequency.
P: 92
 What you are looking for is Shannon-Hartley theorem
Cheers!
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 Quote by r4z0r84 Just thought of how to redesign the inter-net, thanks for all your input. Just one question, Do EM waves travel at the speed of light?
Two things. First, there happens to be a "speed limit" for the universe that we have determined is around 300,000 kilometers per second. This is also known a "c".

Second, this speed happens to be the speed that ALL EM waves travel at, including light. (Light IS an EM wave) They travel at c due to the waves having no rest mass.

Because our primary experience with EM waves is in the visual frequencies, and because they travel at c, we have labelled this value to be "the speed of light".