http://hyperphysics.phy-astr.gsu.edu/Hbase/Sound/refrac.html When sound refracts should we not be able to detect a change in pitch like the doppler effect? (because the wavelength must shorten - hence pitch increase). How do we model refraction - is this a non-linear effect ie it cannot be modeled with a LTI transfer function. Hardy
Refraction of Sound
Started by ●July 12, 2009
Reply by ●July 13, 20092009-07-13
HardySpicer wrote:> http://hyperphysics.phy-astr.gsu.edu/Hbase/Sound/refrac.html > > When sound refracts should we not be able to detect a change in pitch > like the doppler effect?No.> (because the wavelength must shorten - hence > pitch increase).Who told you that? The wavelength of light is shorter in water than in air. That doesn't change its color. I leave it to you to find out why.> How do we model refraction - is this a non-linear > effect ie it cannot be modeled with a LTI transfer function.How do you model any spatial transformation? Acoustic lenses are LTI. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●July 13, 20092009-07-13
On Jul 13, 3:36�pm, Jerry Avins <j...@ieee.org> wrote:> HardySpicer wrote: > >http://hyperphysics.phy-astr.gsu.edu/Hbase/Sound/refrac.html > > > When sound refracts should we not be able to detect a change in pitch > > like the doppler effect? > > No. > > > (because the wavelength must shorten - hence > > pitch increase). > > Who told you that?The above Physics web page! Hardy
Reply by ●July 13, 20092009-07-13
On Jul 13, 3:36�pm, Jerry Avins <j...@ieee.org> wrote:> HardySpicer wrote: > >http://hyperphysics.phy-astr.gsu.edu/Hbase/Sound/refrac.html > > > When sound refracts should we not be able to detect a change in pitch > > like the doppler effect? > > No. > > > (because the wavelength must shorten - hence > > pitch increase). > > Who told you that? The wavelength of light is shorter in water than in > air. That doesn't change its color. I leave it to you to find out why. > > > How do we model refraction - is this a non-linear > > effect ie it cannot be modeled with a LTI transfer function. > > How do you model any spatial transformation? Acoustic lenses are LTI. > > Jerry > -- > Engineering is the art of making what you want from things you can get. > �����������������������������������������������������������������������Ok I assume you are saying that because the speed slows down as well that the overall freq remains constant? Hardy
Reply by ●July 13, 20092009-07-13
On Jul 13, 3:36�pm, Jerry Avins <j...@ieee.org> wrote:> HardySpicer wrote: > >http://hyperphysics.phy-astr.gsu.edu/Hbase/Sound/refrac.html > > > When sound refracts should we not be able to detect a change in pitch > > like the doppler effect? > > No. > > > (because the wavelength must shorten - hence > > pitch increase). >The wavelength of light is shorter in water than in> air. That doesn't change its color.With a prism the light is split at the output though. H.
Reply by ●July 13, 20092009-07-13
Jerry Avins <jya@ieee.org> wrote:> How do you model any spatial transformation? Acoustic lenses are LTI.Optical lenses aren't always LTI. Consider adaptive optics used in newer telescopes and the image stabilization systems now being used in camera lenses. It should be possible to do with acoustic lenses, too. If you hold a helium balloon near your ear it seems quieter. I believe the opposite effect with a CO2 balloon. (Put baking soda an vinegar in a bottle, and put a balloon on top. Sometimes it works better to put the baking soda in the balloon first.) -- glen
Reply by ●July 13, 20092009-07-13
On 13 Jul, 03:58, HardySpicer <gyansor...@gmail.com> wrote:> http://hyperphysics.phy-astr.gsu.edu/Hbase/Sound/refrac.html > > When sound refracts should we not be able to detect a change in pitch > like the doppler effect? (because the wavelength must shorten - hence > pitch increase). How do we model refraction - is this a non-linear > effect ie it cannot be modeled with a LTI transfer function.Refraction is a linear as it gets. The wavelength changes because the speed of sound changes. The frequency is constant. The direction of the sound beam changes because the faster part of the beam 'overtakes' the slower part. Rune
Reply by ●July 13, 20092009-07-13
>On Jul 13, 3:36=A0pm, Jerry Avins <j...@ieee.org> wrote: >> HardySpicer wrote: >> >http://hyperphysics.phy-astr.gsu.edu/Hbase/Sound/refrac.html >> >> > When sound refracts should we not be able to detect a change inpitch>> > like the doppler effect? >> >> No. >> >> > (because the wavelength must shorten - hence >> > pitch increase). >> >> Who told you that? The wavelength of light is shorter in water than in >> air. That doesn't change its color. I leave it to you to find out why. >> >> > How do we model refraction - is this a non-linear >> > effect ie it cannot be modeled with a LTI transfer function. >> >> How do you model any spatial transformation? Acoustic lenses are LTI.The should be some good material on that topic if you Google in relation to acoustic microscopes - e.g. Quate microscopes. We are so used to sound being in the kilohertz range, that its fascinating to see what you can do with sound beyond 1GHz.>> >> Jerry >> -- >> Engineering is the art of making what you want from things you canget.> >Ok I assume you are saying that because the speed slows down as well >that the overall freq remains constant?If you can find a situation where that is not the case I suspect you've invented a time machine. Steve
Reply by ●July 13, 20092009-07-13
HardySpicer wrote:> On Jul 13, 3:36 pm, Jerry Avins <j...@ieee.org> wrote: >> HardySpicer wrote: >>> http://hyperphysics.phy-astr.gsu.edu/Hbase/Sound/refrac.html >>> When sound refracts should we not be able to detect a change in pitch >>> like the doppler effect? >> No. >> >>> (because the wavelength must shorten - hence >>> pitch increase). >> Who told you that? > The above Physics web page!I haven't read the page, but I bet it says only that the wavelength shortens, not that the pitch increases. Why does the wavelength shorten? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●July 13, 20092009-07-13
HardySpicer wrote:> On Jul 13, 3:36 pm, Jerry Avins <j...@ieee.org> wrote: >> HardySpicer wrote: >>> http://hyperphysics.phy-astr.gsu.edu/Hbase/Sound/refrac.html >>> When sound refracts should we not be able to detect a change in pitch >>> like the doppler effect? >> No. >> >>> (because the wavelength must shorten - hence >>> pitch increase). >> Who told you that? The wavelength of light is shorter in water than in >> air. That doesn't change its color. I leave it to you to find out why. >> >>> How do we model refraction - is this a non-linear >>> effect ie it cannot be modeled with a LTI transfer function. >> How do you model any spatial transformation? Acoustic lenses are LTI. >> >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. >> ����������������������������������������������������������������������� > > Ok I assume you are saying that because the speed slows down as well > that the overall freq remains constant?Exactly! In fact, the wavelength shortens _because_ propagation is slower. Since the frequency can't change (why not?) there's no other degree of freedom. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
