Sound Refraction: Does Sound Follow Light Laws?

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Discussion Overview

The discussion centers around the refraction of sound waves and their comparison to light waves, exploring whether sound follows similar laws as light, particularly in terms of reflection and refraction. Participants examine the implications of sound behavior in various environments, including soundproofing and the properties of different materials.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that sound refracts like light, noting similarities in wave behavior, such as reflection and refraction.
  • Others argue that sound can be heard even when doors and windows are closed, suggesting that sound waves can pass through small openings or are not fully blocked by solid objects.
  • A participant mentions that most objects are 'semi-transparent' to sound, requiring special materials for effective soundproofing.
  • Some participants discuss the speed of sound in different media, noting that it increases in water and solids, while light slows down when moving from a less dense to a denser medium.
  • There is mention of seismic waves as a type of sound wave, with references to their refraction providing insights into geological structures.
  • Participants express confusion regarding the differences in behavior between sound and light waves when entering different media, particularly in relation to phase and group velocities.

Areas of Agreement / Disagreement

Participants generally agree that sound and light share wave properties, but multiple competing views remain regarding the specifics of their behavior in different media and the implications of these differences. The discussion remains unresolved on several points, particularly concerning the mechanics of sound refraction compared to light refraction.

Contextual Notes

Some participants express confusion about the terminology related to wave properties, such as group velocity and phase velocity, indicating a potential gap in understanding that may affect the discussion. Additionally, the discussion touches on the complexity of soundproofing materials and their effectiveness, which may depend on various factors not fully explored.

Who May Find This Useful

This discussion may be useful for individuals interested in acoustics, wave physics, soundproofing techniques, and the comparative study of different types of waves.

Raghav Gupta
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Does sound also refract like light?
I know it obeys laws of reflection like that of light ( angle of incidence = angle of reflection)
How we are able to hear sound when there are doors closed, windows closed etc. Light is eventually stopped by opaque high sized objects. So doors should stop longitudinal wave vibration of particles of sound from reaching us?
Also are there any sound proof doors?
I thought earlier that sound doesn't refract but find it's way by some crevices somewhere. Smarty
:DD
 
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Drakkith said:
Absolutely.
Sure. http://www.soundproofing.org/infopages/soundproofing_doors.htm
So can we make all analogies of light to sound except one is transverse wave and other is longitudinal wave.
Can you explain this bit of questions also?
Raghav Gupta said:
How we are able to hear sound when there are doors closed, windows closed etc. Light is eventually stopped by opaque high sized objects. So doors should stop longitudinal wave vibration of particles of sound from reaching us?
 
Note that seismic waves are also a kind of sound waves:
http://en.wikipedia.org/wiki/Seismic_wave
The refraction of these waves gives valuable insight into the structure of the earth.
Also the refraction of ultrasound is used extensively in medical imaging.
 
Raghav Gupta said:
How we are able to hear sound when there are doors closed, windows closed etc. Light is eventually stopped by opaque high sized objects. So doors should stop longitudinal wave vibration of particles of sound from reaching us?

You could say that most objects are 'semi-tranparent' to sound waves, so you need special materials to fully block the sound. Hard, solid objects don't absorb sound very well, while soft materials like foam are very good at absorbing sound.

Raghav Gupta said:
So can we make all analogies of light to sound except one is transverse wave and other is longitudinal wave.
Can you explain this bit of questions also?

Light and sound are both types of waves and will obey all the properties that waves exhibit. Most of what happens to light also happens to sound if you're talking about the wave properties.
 
DrDu said:
Note that seismic waves are also a kind of sound waves:
http://en.wikipedia.org/wiki/Seismic_wave
The refraction of these waves gives valuable insight into the structure of the earth.
Also the refraction of ultrasound is used extensively in medical imaging.
So how does this explain my bit of questions?
I am not asking an insight of earth.
Drakkith said:
You could say that most objects are 'semi-tranparent' to sound waves, so you need special materials to fully block the sound. Hard, solid objects don't absorb sound very well, while soft materials like foam are very good at absorbing sound.
Light and sound are both types of waves and will obey all the properties that waves exhibit. Most of what happens to light also happens to sound if you're talking about the wave properties.
This was valuable info. Thanks.
 
One of the first effects that was explained using the refraction of sound waves was the observed audibility of canon sound over large distances by Chladni and others at the beginning of the 19th century. Canon sound from a military operation could be heard up to 50 km away and then again in a distance of 120 km up to 250 km. The second zone of audibility is due to sound getting refracted in higher zones of the atmosphere in inversion layers.
 
Yeah this makes sense to me
But
How speed of sound increases in water and of light decreases , if they both have wave properties @Drakkith and @DrDu ?
 
Please don't tag me if I'm already in the discussion. I don't have time to answer right now. Someone else might be able to help you in the meantime.
 
  • #10
The speed of light increases both for sound waves and for light waves. However, you have to be careful here which speed you are talking of. The relevant speed to explain refraction is phase velocity, i.e. the speed with which the maxima in a sinusoidal sound wave travel. This speed is different from the group velocity which describes the speed of a wavepacket and is relevant to information transport. For a sound wave, the two velocities differ little, but for a light wave, phase velocity is higher in a medium than in vacuum while group velocity is always smaller.
 
  • #11
Doesn't know the basics of group velocity or phase velocity.
Was finding Wikipedia a bit jargon.
The speed here that I am asking is
that sound speed in air is around 340 m/s and in water it increases and in solids further more.
But for light
Light when refracts from a rarer to denser medium it speed decreases like in water from air.
Light speed in air is c but it is decreasing when refracting?
 
  • #12
Sorry, I got somewhat confused. You are right: in most media, the phase speed of light is in deed less than the speed of light in vacuo. So if you want, light behaves here different than sound waves, at least when passing from air to some solid material.
 
  • #13
Now Drakkith was saying that if considering waves they have same properties.
So how in this case the two behaving differently?
 
  • #14
They behave the same, but parameters are different. Even for light, the refractive index n is different for different wavelengths. So it shouldn't be too astonishing that n may have different values (<1 vs >1 ) for different kind of waves.
 
  • #15
Yeah thanks but wanting a bit more explanation.
 
  • #16
Raghav Gupta said:
Now Drakkith was saying that if considering waves they have same properties.
So how in this case the two behaving differently?

That is close, but not exactly what I said. I said that light and sound both obey all the properties that waves exhibit, meaning that both light and sound undergo refraction, diffraction, have a wavelength/frequency, etc. The reason light and sound behave differently when entering a medium is that they are both very different waves.

See the following article for an explanation of the speed of sound in a medium: http://en.wikipedia.org/wiki/Speed_of_sound#Basic_concept

Light is composed of alternating electric and magnetic fields, which have very different rules in a medium. In free space, the EM wave (light) has nothing to interact with. But in a medium, the wave interacts with large numbers of charged particles.

See the following links:
http://en.wikipedia.org/wiki/Speed_of_light#In_a_medium
https://www.physicsforums.com/threads/do-photons-move-slower-in-a-solid-medium.511177/#post-899393
 
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  • #17
Thanks, got it a bit.
As there is a vast explanation. Will look to it afterwards one by one.
 

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