Why do concerts not impact the way we see light?

In summary, the acoustic-optic effect is confirmed to be present in air, but it is very weak and unlikely to be observed in a concert setting.
  • #1
ThunderLight
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If concert environments are saturated with sound, why don't we witness a change in light colours (frequency shift) or reflection or any other effect witnessed in laboratory experiments documenting acoustic-optic effects?
 
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  • #2
Those acousto-optical effects require that both the light and the sound be traveling through specific mediums such as ultrasonic gratings. Light and sound do not normally interact significantly in the air at a concert.
 
  • #3
Drakkith said:
Those acousto-optical effects require that both the light and the sound be traveling through specific mediums such as ultrasonic gratings. Light and sound do not normally interact significantly in the air at a concert.

That's what I originally thought. However, an IEEE paper and other papers did experiments on the interaction in air. So this further confused me. - For those who can't access the paper in IEEE - It is a paper which reports the measurements of Sound Pressure via the acoustic-optic effect in air with a laser. And the interaction is confirmed.
 
  • #4
I can't read the full text, but I think the authors just measured the amount of acousto-optical effect the air has. I expect it is very low.
 
  • #5
Drakkith said:
I can't read the full text, but I think the authors just measured the amount of acousto-optical effect the air has. I expect it is very low.

The conclusion of the paper says: "Sound pressure was able to be measured by a laser doppler velocimeter through the optical phase modulation due to the acoustic-optic effect of air"

So it's not so insignificant as to not cause any phase change.

But perhaps not strong to influence the frequency.
 
  • #6
[PLAIN]https://en.wikipedia.org/wiki/Acousto-optics said:
In[/PLAIN] general, acousto-optic effects are based on the change of the refractive index of a medium due to the presence of sound waves in that medium. Sound waves produce a refractive index grating in the material, and it is this grating that is "seen" by the light wave.[6] These variations in the refractive index, due to the pressure fluctuations, may be detected optically by refraction, diffraction, and interference effects,[7] reflection may also be used.

Neat stuff, but I think the answer is simple. Laser measurements can be much more sensitive than human sensory organs.
 
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  • #7
If you want to see an opto acoustic effect, stand at some distance from a crt computer monitor (several metres) and whistle or hum. It can often produce the impression of moving bars on the display. The effect needs a scanned display, in my experience and doesn't seem to work up close (for me). It's not Physics, tho'. It's in your head.
 
  • #8
sophiecentaur said:
. It's not Physics, tho'. It's in your head.

That sounds cool. Do you mean that it makes your eyes bounce up and down?

Like everything else human, I believe that human abilities vary widely between individuals. I've heard that artists can be trained to resolve more colors than most people. I'm not surprised that some people can see stroboscopic effects that others can't see.

It is also a good age test. If you know what the horizontal hold and vertical hold knobs on a TV were for, you are an old fart. :woot:
 
  • #9
anorlunda said:
Do you mean that it makes your eyes bounce up and down?
I think so. I noticed it when eating crunchy stuff in front of some displays. Or when when using an electric tooth brush.
 
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  • #10
ThunderLight said:
If concert environments are saturated with sound, why don't we witness a change in light colours (frequency shift) or reflection or any other effect witnessed in laboratory experiments documenting acoustic-optic effects?

You need higher intensity to see those with the naked eye:

http://images.slideplayer.com/21/6283886/slides/slide_27.jpg

Click on image below for full scale:

HMnow.jpg
More discussion:
http://physics.stackexchange.com/qu...adient-in-a-shock-wave-of-supersonic-aircraft
 
  • #11
The paper mentions that they use "a strong ultrasonic field" to measure the effect.
The measured value of the acoustic pressure was 610 Pa.
For a sound in air this corresponds to an intensity of about 460 W/m^2 or over 145 decibels.
This level is unlikely to be encountered in a concert hall, even if it's a hard rock band.
But even at this level you need a sensitive instrument to measure the Doppler shift. They are talking about velocities produced by the sound in the order of mm/s.
 
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1. Why does the lighting at concerts not affect our perception of light?

The lighting at concerts is designed to enhance the visual experience for the audience and create a certain atmosphere, but it does not significantly impact our perception of light because it is not the primary source of light in the environment. The main source of light at concerts is typically stage lights, while our primary source of light perception is natural light from the sun or artificial light from room lighting.

2. Can the lighting at concerts affect our vision in any way?

While the lighting at concerts may not affect our perception of light, it can have other effects on our vision. For example, excessively bright or flashing lights can cause temporary vision impairment or discomfort for some individuals. It is also important to note that prolonged exposure to bright lights can have potential long-term effects on our eyesight.

3. How do our eyes adjust to the changing lighting at concerts?

Our eyes have a natural ability to adjust to changing lighting conditions, and this includes the lighting at concerts. The muscles in our irises contract or expand to control the amount of light that enters the eye, allowing us to see clearly in different lighting environments. This process is called pupillary reflex.

4. What role does contrast play in our perception of lighting at concerts?

The contrast between the lighting and dark areas of the concert venue can affect our perception of the lighting. For example, if the stage is brightly lit and the rest of the venue is dim, our eyes may struggle to adjust and we may perceive the lighting differently. This is why lighting technicians carefully consider the contrast and balance of light throughout the concert.

5. Is there a difference in how different colored lights impact our vision at concerts?

Different colored lights may have different effects on our vision at concerts. For example, red lights may make it more difficult to see details, while blue lights may enhance our ability to see certain colors. However, the overall impact on our vision is still minimal, as the lighting at concerts is not the primary source of light for our perception.

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