Can Sound Be Captured Like a Photograph?

[Logs]

Is there any sensor or method that allows a 'photo' to be taken of sound from different places? Similar to an ultrasound that is used in the medical field, but can be used more like a camera. I know about Schlieren Imaging but I'm thinking more like a map of all the sounds at a moment, maybe even with color coding for different pitch sounds?

 

[Baluncore]

If you had an array of microphones you could synchronously record all the audio, then synthesise an image using interferometry as is done with VLBI radio astronomy. Because the attenuation of sound is frequency dependent you will get different pictures at different wavelengths and ranges. Wind will also distort the image.

The beam pattern of the array will be highly wavelength dependent. I expect that image generation will rely very heavily on the FFT of the data.

Long distance audio pictures of the landscape will be low frequency only. Ultrasonic images may be possible over tens of metres. For example; a directional ultrasound microphone can be used to identify corona discharge or breakdown of insulators on electrical power lines.

 

[anorlunda]

Your description sounds like the seismic methods used in oil exploration.

 

[ZapperZ]

Is there any sensor or method that allows a 'photo' to be taken of sound from different places? Similar to an ultrasound that is used in the medical field, but can be used more like a camera. I know about Schlieren Imaging but I'm thinking more like a map of all the sounds at a moment, maybe even with color coding for different pitch sounds?

But an ultrasound is not an image of sound! It is an image of objects that reflect the sound waves. Saying that it is an image of sound is similar to saying that objects that we see when we switch on light is an image of light.

If what you want is to detect the intensity or loudness of sound with respect to spatial position, then as has been suggested, you will need an array of microphones. Otherwise, you will have to define what you really want.

Zz.

 

[Baluncore]

Seismic surveys map 3D underground structures. The seismic waves are refracted and reflected by the structures, the waves do not travel in straight lines but by many paths. Given a single impulse, the software must solve for the 3D structure based on the return of energy via many paths to each of the several geophones on the surface.

Like seismic reflection, radar and sonar transmit a signal and produce an image of the reflectors. They do not image multiple remote sources of energy.

Interferometry has the advantage of a more isotropic propagation medium so it can reconstruct an image of the multiple sources of remote sound excitation. It may be possible to sharpen the image by deconvolving the intervening atmospheric distortions.

Acoustic direction finding was used during WW1 and WW2 for gun and aircraft location. It did not produce an image, just a direction. See the four pictures here. https://en.wikipedia.org/wiki/Acoustic_location
https://en.wikipedia.org/wiki/Acoustic_location
There is some work on acoustic DF taking place today. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134470/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134470/

Acoustic imaging should be able to highlight the sources of sounds and superimpose them on a visual camera image. It should also be possible to separate out the individual conversations in a crowd by optimising multiple synthesised acoustic spot beams.

Imagine a visual image of a highway with the noise from individual vehicles superimposed in real time, tracking the vehicles as they move. If the array is large enough there will be doppler information available.

a map of all the sounds at a moment

The image will not be made at “a moment” in time. It will be the accumulation of energy over a period of time. I would expect a minimum of 10 seconds recording since low frequencies are involved and full cycles of sound are needed to correlate the different channels and straddle the receive array.

 

[anorlunda]

But an ultrasound is not an image of sound! It is an image of objects that reflect the sound waves.

That's a good point. @Logs, can you clarify your question.

 

[CWatters]

The sound pressure waves caused by supersonic airflow in a wind tunnel can be imaged but I haven't looked to see how they do it. Perhaps something to do with pressure changes causing the refractive index to change??

https://goo.gl/images/wkSmJ5

 

[Drakkith]

The sound pressure waves caused by supersonic airflow in a wind tunnel can be imaged but I haven't looked to see how they do it. Perhaps something to do with pressure changes causing the refractive index to change??

https://goo.gl/images/wkSmJ5

Yes, that's exactly it CWatters.
See here: https://en.wikipedia.org/wiki/Shadowgraph
And here: https://en.wikipedia.org/wiki/Schlieren_photography

However, the OP isn't interested in this method. See post #1.

 

[CWatters]

Is there any sensor or method that allows a 'photo' to be taken of sound from different places? Similar to an ultrasound that is used in the medical field, but can be used more like a camera. I know about Schlieren Imaging but I'm thinking more like a map of all the sounds at a moment, maybe even with color coding for different pitch sounds?

Most sound waves aren't standing waves so i think you would have the same colour everywhere unless you make the brightness proportional to the loudness.

Perhaps think up a scenario and make a drawing by hand showing what you want it to look like?

 

[sophiecentaur]

And here: https://en.wikipedia.org/wiki/Schlieren_photography

Hot dang. You beat me to it!

 

[f95toli]

There are at least a couple of ways to map free-field pressure waves( i.e. sound) , both use lasers: acousto-optic measurements using a vibrometer; and photon correlation spectroscopy.

Here is a link with a description of the former
https://www.theverge.com/2011/11/8/2545157/national-physical-laboratory-visualize-sound-lasers

http://www.npl.co.uk/commercial-services/sectors/advanced-manufacturing/laser-based-acousto-optic-mappingIs this the kind of thing the OP was referring to?

 

[anorlunda]

The OP hasn't been heard from since #1.