# Can sound be refracted? **URL:** \ **Category:** Factual Questions\ **Created:** [November 9, 2002, 10:21am UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011 "2002-11-09T10:21:41Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![starman](https://avatars.discourse-cdn.com/v4/letter/s/8c91f0/32.png) [@starman](https://boards.straightdope.com/u/starman)\ **Post date:** [November 9, 2002, 10:21am UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/1 "2002-11-09T10:21:41Z")
Can sound be refracted? It can certainly be reflected, so does sound bend at the interface of mediums of different densities? -Oli ---
**Author:** ![Urban\_Ranger](https://avatars.discourse-cdn.com/v4/letter/u/e9c0ed/32.png) [@Urban\_Ranger](https://boards.straightdope.com/u/Urban_Ranger)\ **Post date:** [November 9, 2002, 11:09am UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/2 "2002-11-09T11:09:37Z")
Sure. Actually, sounds refract inside the atmosphere itself. ---
**Author:** ![privard](https://avatars.discourse-cdn.com/v4/letter/p/e8c25b/32.png) [@privard](https://boards.straightdope.com/u/privard)\ **Post date:** [November 9, 2002, 12:57pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/3 "2002-11-09T12:57:14Z")
Urban–I’d love to hear more. Examples or explanations? What happens when sound refracts? This is pretty interesting. ---
**Author:** ![Cartooniverse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cartooniverse/32/3084_2.png) [@Cartooniverse](https://boards.straightdope.com/u/Cartooniverse)\ **Post date:** [November 9, 2002, 1:00pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/4 "2002-11-09T13:00:04Z")
Sure. Prime example: You’re sitting there in your doidies, scratching yourself and sipping from an ice cold Duff Beer. You are watching the NFL Game Of The Week, or whatever. You see those folks on the sidelines with the white dishes, like small home dish antenna held on their sides? They are parabolic antennae. They are used to capture sounds generated far off, and focus on just one nodal point. The sound is bounced ( refracted ) off of the precisely curved surface of the parabolic dish, back towards a small microphone sitting in it’s absolute middle. That’s how you can hear the Quarterback, cursing under his breath. Sound is refracted moment to moment. But I have to admit that your use of THAT word begs a deeper examination. I have defined a reflective situation, and the sound is bent backwards by the dish’s curved surface. Did you mean more a situation where sound is altered in a fundamental way, a la light through a prism? If that is the case, then I might offer the amusing game of screaming underwater. It seems to me that the density of the water refracts the sound waves. I can hear you scream underwater, but it isn’t a volume issue, you would SOUND differently than you would above the surface of the water. ( Unless you were the Wifestrocity, in which case your voice would be no less shrill. :rolleyes: ). Is that more what you had in mind? As much a bending as a pure reflection with little distortion or alteration? I would alledge that sound is refracted every time it is reproduced by a set of stereo speakers, but that’s just my WAG. Cartooniverse ---
**Author:** ![flex727](https://avatars.discourse-cdn.com/v4/letter/f/258eb7/32.png) [@flex727](https://boards.straightdope.com/u/flex727)\ **Post date:** [November 9, 2002, 3:15pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/5 "2002-11-09T15:15:59Z")
> [@](#): > > \*Originally posted by starman \* > \*\*Can sound be refracted? It can certainly be reflected, so does sound bend at the interface of mediums of different densities? > -Oli \*\* Absolutely. Sound is a wave. All waves possess the basic properties of reflection, refraction, diffraction, and interference. Anytime a wave moves from a medium of one index to one of another, refraction occurs. The index of refraction is a function of the speed of the wave in that medium. ---
**Author:** ![Yossarian](https://avatars.discourse-cdn.com/v4/letter/y/9de0a6/32.png) [@Yossarian](https://boards.straightdope.com/u/Yossarian)\ **Post date:** [November 9, 2002, 3:44pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/6 "2002-11-09T15:44:18Z")
[Here’s](http://www.physics.nwu.edu/ugrad/vpl/optics/snell.html) a demonstration of Snell’s Law, which models the angle of refraction. ---
**Author:** ![Yossarian](https://avatars.discourse-cdn.com/v4/letter/y/9de0a6/32.png) [@Yossarian](https://boards.straightdope.com/u/Yossarian)\ **Post date:** [November 9, 2002, 3:45pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/7 "2002-11-09T15:45:22Z")
…and a [description](http://www.glenbrook.k12.il.us/gbssci/phys/Class/refrn/u14l2b.html) of Snell’s law to go with it! ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 9, 2002, 8:59pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/8 "2002-11-09T20:59:23Z")
There was an example of this at the Exploratorium in Frisco years ago (don’t know if it’s still there). They has a big weather balloon filled with carbon dioxide which is denser than air. It acted like a primitive sound lens. If you stood directly opposite someone supposedly you could converse in whispers. I was alone and couldn’t really try. The people that did, didn’t know how to do it right so they didn’t seem impressed. Sound can also be diffracted. Useful in acoustic design since sometimes you want to pass/reflect certain frequencies. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [November 9, 2002, 10:35pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/9 "2002-11-09T22:35:36Z")
Sure it can. This site is a [speed of sound calculator](http://www.measure.demon.co.uk/Acoustics_Software/speed.html) for standard atmospheric pressure and a typical CO[sub]2[/sub] concentration. Under those conditions the speed of sound varies with temperature and humidity. So if a sound wave is obliquely approaching a region of temperature discontinuity, say going from cold to hot at the boundry of a temperature inversion , it will speed up. So the part of the wave reaching the boundry first will speed up and the wave will be bent. ---
**Author:** ![bbeaty](https://avatars.discourse-cdn.com/v4/letter/b/c0e974/32.png) [@bbeaty](https://boards.straightdope.com/u/bbeaty)\ **Post date:** [November 10, 2002, 5:36am UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/10 "2002-11-10T05:36:25Z")
Horizontal sound normally refracts upwards. Air isn’t a uniform medium; it’s denser at low altitude. If you fire a huge cannon during WWII, people a certain number of miles distant can’t hear it. The sound waves bend upwards, so beyond a certain distance there is a “zone of silence” in a ring around the source of sound. But people much farther away CAN hear the boom since the upward-refracted sound often reflects from high altitude layers of temperature discontinuity and heads back downwards. ---
**Author:** ![Urban\_Ranger](https://avatars.discourse-cdn.com/v4/letter/u/e9c0ed/32.png) [@Urban\_Ranger](https://boards.straightdope.com/u/Urban_Ranger)\ **Post date:** [November 10, 2002, 7:17am UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/11 "2002-11-10T07:17:35Z")
Another factor you need to consider is temperature. While air near the ground is denser, it is also hotter. So whether sound waves refract upwards or downwards really depend on the local conditions. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [November 10, 2002, 12:37pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/12 "2002-11-10T12:37:16Z")
> [@](#): > > \*Originally posted by Cartooniverse \* > **Sound is refracted moment to moment. But I have to admit that your use of THAT word begs a deeper examination. I have defined a reflective situation, and the sound is bent backwards by the dish’s curved surface.** I guess you’re claiming that reflection is a refraction? ---
**Author:** ![Cartooniverse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cartooniverse/32/3084_2.png) [@Cartooniverse](https://boards.straightdope.com/u/Cartooniverse)\ **Post date:** [November 10, 2002, 1:41pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/13 "2002-11-10T13:41:56Z")
Now now, let’s keep it friendly. I dunno about claiming. I may have mistakenly overlapped the two concepts. How do you differentiate? I mean, the dish I described reflects the sound back into the nodal point, where the mic head is. Isn’t that also altering the angle of the waves, and is that refraction as well? Under water, as mentioned above, isnt’ the sound refracted more than reflected because it is moving THROUGH the water and being distorted by said water? Or, could you argue that it is also being purely reflected since the water molecules are causing the sound waves to bounce back and forth as they move in a straight line? You tell me. The Winter Garden lobby at #7 World Trade Center used to have a wonderful standing exhibit. They were two granite blocks that were basically meant as wide seats. The " back" of each seat was a parabola. The two were set across the immense open air space of the Atrium there. You sat and had a normal quiet conversation with the person 100 feet or more away from you. YOUR voice was reflected/refracted by the granite parabola that was the back seat of the other person’s chair. And their voice was reflected/refracted just behind you. Your head rested at the nodal point. Amazing how little head movement it took for the sounds to become unintelligible. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [November 10, 2002, 1:51pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/14 "2002-11-10T13:51:38Z")
> [@](#): > > \*Originally posted by Cartooniverse \* > **Now now, let’s keep it friendly.** ??? ---
**Author:** ![Cartooniverse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cartooniverse/32/3084_2.png) [@Cartooniverse](https://boards.straightdope.com/u/Cartooniverse)\ **Post date:** [November 10, 2002, 1:54pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/15 "2002-11-10T13:54:02Z")
I wasn’t ‘claiming’ anything. I was trying to suss out how the overlap worked- if there IS an overlap- in the ideas of refraction opposed to reflection. And, I was being sarcastic with a smile on my face. No offense intended, to be sure. ---
**Author:** ![flex727](https://avatars.discourse-cdn.com/v4/letter/f/258eb7/32.png) [@flex727](https://boards.straightdope.com/u/flex727)\ **Post date:** [November 10, 2002, 11:39pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/16 "2002-11-10T23:39:42Z")
> [@](#): > > \*Originally posted by Cartooniverse \* > \*\*I wasn’t ‘claiming’ anything. I was trying to suss out how the overlap worked- if there IS an overlap- in the ideas of refraction opposed to reflection. > > And, I was being sarcastic with a smile on my face. No offense intended, to be sure. \*\* There is no overlap. Reflection is a wave bouncing off an interface and refraction is what happens when the wave passes _through_ an interface. For transparent media, both will usually occur. ---
**Author:** ![Cartooniverse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cartooniverse/32/3084_2.png) [@Cartooniverse](https://boards.straightdope.com/u/Cartooniverse)\ **Post date:** [November 11, 2002, 3:43am UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/17 "2002-11-11T03:43:06Z")
Okay, I understand that. If you are under water, is the sound of your scream being reflected against the water molecules, or refracting through the liquid medium? ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [November 11, 2002, 4:30am UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/18 "2002-11-11T04:30:54Z")
Propagating? ---
**Author:** ![Cartooniverse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cartooniverse/32/3084_2.png) [@Cartooniverse](https://boards.straightdope.com/u/Cartooniverse)\ **Post date:** [November 18, 2002, 5:05pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/19 "2002-11-18T17:05:04Z")
Huh? ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [November 18, 2002, 5:27pm UTC](https://boards.straightdope.com/t/can-sound-be-refracted/136011/20 "2002-11-18T17:27:50Z")
Refraction and reflection only occur where there the wave encounters different material. If you are just talking about sound travelling through water (uniform medium), it’s simply propagating. It’s neither reflecting nor refracting. If the wave hits the surface of the water (i.e. boundary between water and air), some of the wave gets _reflected_ back into the water, and some of it gets _refracted_ into the air.