Total internal reflection with Sound?

In summary, this article discusses how sound waves can be reflected to hide submarines beneath/above different layers of water.
  • #1
Chaos' lil bro Order
683
2
In Diamonds, light that enters gets trapped within due to total internal reflection, defined as:

Total internal reflection is an optical phenomenon that occurs when a ray of light strikes a medium boundary at an angle larger than the critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary no light can pass through, so effectively all of the light is reflected. The critical angle is the angle of incidence above which the total internal reflection occurs.

Diamonds have one of the highest index of refractions there is at a whopping n = 2.41.

I'm curious to know if there is a material or apparatus that can achieve the same effect as a diamond, but for sound waves instead of light.
 
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  • #2
Good question. Since sound waves are waves, they obey the laws of refraction (Snell's Law) just like light. You can basically achieve total internal reflection of sound in any medium as long as it is transmitting into a faster medium above the critical angle for that boundary. For example sound travels faster in hotter air. This means if sound was moving from cold air to hot air at a shallow angle to the boundary, you would have the total internal reflection of sound.

You could even have it traveling from air (340m/s) to water (1500m/s)

I'm not sure there are any practical applications for this effect.
 
  • #3
jaseh86 said:
I'm not sure there are any practical applications for this effect.
Hiding submarines?
Layers of different salinity and temperature (haloclines and thermoclines) have different densities anddifferent speeds of sound. Sonar pulses bounce off the interface between the layers allowing submarines tohide beneath/above them.
Not sure if this is really TIR or just reflection from an impedence mismatch - but it is usefull
 
  • #4
mgb_phys said:
Hiding submarines?
Layers of different salinity and temperature (haloclines and thermoclines) have different densities anddifferent speeds of sound. Sonar pulses bounce off the interface between the layers allowing submarines tohide beneath/above them.
Not sure if this is really TIR or just reflection from an impedence mismatch - but it is usefull

Very interesting comments. mgb points out an example with submarines, this sounds quite fascinating, I shall look it up. Thanks.
 

1. What is total internal reflection with sound?

Total internal reflection with sound is a phenomenon where sound waves that are traveling through a medium hit a boundary at a certain angle and are completely reflected back into the same medium. This occurs when the angle of incidence is greater than the critical angle, which is dependent on the speed of sound in the two media.

2. How does total internal reflection with sound occur?

Total internal reflection with sound occurs when sound waves encounter a boundary between two mediums at an angle greater than the critical angle. This causes the sound waves to be completely reflected back into the same medium, rather than being transmitted into the second medium.

3. What are some real-life examples of total internal reflection with sound?

One example of total internal reflection with sound is the phenomenon of whispering galleries, where sound waves are reflected off the curved walls of a building and can be heard clearly at a distant point. Another example is the use of underwater sonar, where sound waves are reflected off the surface of the ocean to detect objects or terrain.

4. How is total internal reflection with sound different from total internal reflection with light?

Total internal reflection with sound and light are both caused by the same principle of encountering a boundary at an angle greater than the critical angle. However, sound waves travel much slower than light waves, so the critical angle and conditions for total internal reflection are different for sound waves compared to light waves.

5. What are the applications of total internal reflection with sound?

Total internal reflection with sound has several practical applications, such as in the design of acoustic mirrors and lenses, which can focus sound waves. It is also utilized in medical imaging techniques like ultrasound, as well as in underwater communication and navigation systems.

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