On 13 Jul, 22:53, HardySpicer <gyansor...@gmail.com> wrote:
> Yes it was more the sound at the output I was interested in than in
> the medium itself.
> You have answered my question I think. If I take a loudspeaker and
> attatch it to a cavity filled with a gas I can shift the frequencies
> right?
It depends on the sound you use to excite the cavity.
If the loudspeaker emits a steady-state tone, then no,
you don't see any changes in frequency in the cavity.
The gas will vibrate at the same frequency as the
steady-state tone.
If the loudspeaker emits impulses, then the cavity
will resonate at a different frequency than it would
if it was filled with air. This is the reason why
people get 'Mickey Mouse voices' when they breathe
helium. The voice cords emit impulses at the same
rate as in air, but the resonance in the vocal tract
occurs at a different frequency because the gas
has different compressibility and density than air.
Rune
Reply by HardySpicer●July 13, 20092009-07-13
On Jul 13, 4:24�pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
> Jerry Avins <j...@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
Yes it was more the sound at the output I was interested in than in
the medium itself.
You have answered my question I think. If I take a loudspeaker and
attatch it to a cavity filled with a gas I can shift the frequencies
right?
Hardy
Reply by Rune Allnor●July 13, 20092009-07-13
On 13 Jul, 19:13, Jerry Avins <j...@ieee.org> wrote:
> Jerry Avins wrote:
> > Richard Owlett wrote:
> >> Jerry Avins wrote:
> >>> 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).
>
> >>>> 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.
>
> >>> That's because the degree of refraction varies with wavelength. So what?
>
> >>> Jerry
>
> >> Should we add birefringence effects?
>
> > Think parallel planes.
>
> Forget that nonsense. How can you make polarized compression waves?
'Sound' is an arbitrary term, that traditionally relates
to audio. From a purely technical POV, both compressional
waves and shear waves obey the same physical laws. Wave
splitting due to polarizations have been observed in seismic
data. Some people have suggested to use this effect as a
classifier of the geophysical medium. The only problem
with that is that polarization can be caused by several
independent effects, like cracks and fractures, or fine-scale
layering in sedimentary rocks.
Rune
Reply by Jerry Avins●July 13, 20092009-07-13
Jerry Avins wrote:
> Richard Owlett wrote:
>> Jerry Avins wrote:
>>> 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).
>>>>
>>>> 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.
>>>
>>>
>>> That's because the degree of refraction varies with wavelength. So what?
>>>
>>> Jerry
>>
>> Should we add birefringence effects?
>
> Think parallel planes.
Forget that nonsense. How can you make polarized compression waves?
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Jerry Avins●July 13, 20092009-07-13
glen herrmannsfeldt wrote:
> Jerry Avins <jya@ieee.org> wrote:
>
>> 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?
>
> Maybe someone is mixing up refraction and the doppler effect.
>
> Doppler changes frequency, refraction doesn't.
Yes. I think I encourages Spicer to understand that for himself.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Jerry Avins●July 13, 20092009-07-13
Richard Owlett wrote:
> Jerry Avins wrote:
>> 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).
>>>
>>> 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.
>>
>>
>> That's because the degree of refraction varies with wavelength. So what?
>>
>> Jerry
>
> Should we add birefringence effects?
Think parallel planes.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by glen herrmannsfeldt●July 13, 20092009-07-13
Jerry Avins <jya@ieee.org> wrote:
> 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?
Maybe someone is mixing up refraction and the doppler effect.
Doppler changes frequency, refraction doesn't.
-- glen
Reply by Richard Owlett●July 13, 20092009-07-13
Jerry Avins wrote:
> 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).
>>
>> 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.
>
>
> That's because the degree of refraction varies with wavelength. So what?
>
> Jerry
Should we add birefringence effects?
Reply by Clay●July 13, 20092009-07-13
On Jul 12, 9:58�pm, 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.
>
> Hardy
Hello Hardy,
The webpage you cite does say the frequency remains constant.
Hyperphysics is a very informative site - I'm glad you are referring
to it. I know the author personally - he spent quite a bit of time
putting it all together. He (Dr. Rod Nave) is retired now. I had
several classes with him.
Clay
Reply by dbd●July 13, 20092009-07-13
On Jul 12, 8:56 pm, HardySpicer <gyansor...@gmail.com> 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!
>
> Hardy
Hardy
Try reading your own source:
"it is clear that a slower speed must shorten the wavelength since the
frequency of the wave is determined by its source and does not
change."
Dale B. Dalrymple