Imaging sound waves with infrared or even microwave sensor

[kos]

0

down vote

favorite

Can you see sound wave propagating trhough very hot air (500 -1000 degree celcius ) Why so much ? To be more distinguishable than a natural emitters since everything we know emits some radiation if it is over absoulute zero temperature.So if you look at the air by infrared or even microwave camera. I suppose that somebody will see direclty the propagation of the changing pressure as acoustic wave. If we can imagine for instance how it looks sound propagating in water and we can directly see the changes of pressure so it should be the same case with the air. But it is difficult to see the sound wave direclty with a naked eye as air is transperant for wavelenghts of visible light where is our visible perception. So if we look trhough the objective of a infrared camera we will detect the emitted not reflected radiation as it is the case of our natural perceotion. So when the sound wave propagates trhough medium in our case air and since we can see the emission of infrared radiation easily of our medium (air) so I suppose we will see direclty by the infrared camera the sound ! Am I correct ?

[EdEarl]

It may be possible, as sound travels in air, it compresses a volume of air, which should cause it to heat up slightly. Alternately, sound decompresses the same volume, which should cause it to cool slightly. I didn't find a reference via Google, but only made a quick search. Someone else here may know more.

[Strange]

Yes: using Schlieren Flow Visualization

http://www.npr.org/2014/04/09/300563606/what-does-sound-look-like

[swansont]

!

Moderator Note

Please don't copy-paste questions from other sites.

[kos]

I coppy paste from other site my question I have asked there but without proper answer !

Yes: using Schlieren Flow Visualization

http://www.npr.org/2014/04/09/300563606/what-does-sound-look-like

1

Thank you. I know a little bit for this idea but I asked because in the case of my question it is not the objcet that we imaging illuminated by the light from some source like in the video with light bulb but it is the emitter it is the source of light itself.Hot air realising its hotness in a manner of electromagnetic radiation is the direct source of incoming light into the focus of camera. Would it this method still be applicable?

[Strange]

Are you asking if the sound travelling through the air can, by itself, generate detectable electromagnetic radiation?

 

I don't know the answer to that... but it is clear that sound must provide some energy to the air and heat it slightly. Some analysis here:

http://www.physicscentral.com/explore/poster-coffee.cfm

Edited April 4, 2016 by Strange

[kos]

Yes I have asked e

Are you asking if the sound travelling through the air can, by itself, generate detectable electromagnetic radiation?

 

I don't know the answer to that... but it is clear that sound must provide some energy to the air and heat it slightly. Some analysis here:

http://www.physicscentral.com/explore/poster-coffee.cfm

exaclty the same .But gas as everything around us radiates naturally in infrared,microwave,radio or any other type of frequency depending on the temperature . So if the temperature of some volume of air is higher than the temperature around this volume because for instance the first volume is constantly warmed by some some source of heat as fire , then if we look trhough microwave remote sensing camera or thermal imaging one we will see the difference in brightness bwteen both regions. So if somebody talks you can probably see the disturbance cause by the speech as a wave pattern by the natural emissivity of the hotter air.

I use hotter and colder regions of air in relavence of each other because the hotter spot can be easly distinguishable from the rest of the surrounding medium wich temperature is expected to be in almost the same interval and the emmission of the objects from medium would be difficult for deffentiate since their temperature are close to each other and so their electromagnetic emission should be almost the same but not in comparison of the much warmer object as flame from the candle

[EdEarl]

The best infrared cameras cool the infrared detector chip to eliminate some of the infrared noise, and thereby it is a better detector. Infrared detectors work better when the source of infrared they see is warmer than the detector.

[Mordred]

On that note, an old friend of mine was doing a study on kinetic energy in falling objects. He had a plate he cooled to the same baseline temperature then dropped different mass objects onto the plate and recorded the temperature via a highly sensitive infrared camera.

 

Obviously there being lots of room for systematic errors this took a while.

However it was fun looking through that camera. You could see every single footprint long after people left the room lol.

[kos]

My main question is still there. What if the invistigated object is the emitter?

[EdEarl]

Any camera picks up both emitted and reflected light/infrared (EMR). Better cameras will pick up lower levels of EMR. It's really about how much you want to spend on a camera, whether or not it detects what you want it to. The inexpensive security cameras need infrared light to illuminate the scene.

 

IDK if this camera will do what you need, its specifications include the following:

 

Exceptional thermal sensitivity of < 0.02°C at +30°C

It is necessary to find out how much temperature change in air occurs from acoustic waves.

Edited April 5, 2016 by EdEarl