Re: New question about Longitudinal sound waves?

On Apr 16, 12:15 pm, "Randy Poe" <poespam-t...@xxxxxxxxx> wrote:
On Apr 16, 12:07 pm, "g...@xxxxxxxxxxx" <g...@xxxxxxxxxxx> wrote:





On Apr 16, 3:04 am, "g...@xxxxxxxxxxx" <g...@xxxxxxxxxxx> wrote:

On Apr 15, 12:19 pm, "OG" <o...@xxxxxxxxxxxxxxxxxxx> wrote:

"OG" <o...@xxxxxxxxxxxxxxxxxxx> wrote in message

news:58f0utF2go2khU1@xxxxxxxxxxxxxxxxxxxxx

<g...@xxxxxxxxxxx> wrote in message
news:1176648165.971180.107640@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Tom Roberts said:

"First off, sound can be transverse waves in a medium
which supports transverse waves -- air does not, but a steel bar can
and
does: suspend a steel bar loosely along a horizontal axis, then
strike
it at one end transversely from the top with a hammer -- it will
vibrate
and ring; now place your finger on the top of the bar and feel it
vibrate transversely (your finger is insensitive to longitudinal
vibrations)."
****************************************************************

A speaker is like a hammer hitting an air molecule which then hits
another longitudinaly and then reaches the ear drum.

But this alone is insufficient, for we would hear only if we were
standing in line with the direction of the propagation therefore:

1. Due to inner-collision momentum (action/reaction) between air
molecules, we also here sound coming from the back of the
speaker....this is also longitudinal.

2. But we also here the sound, above, below, to the left, right thus
most likely because the air molecules are not perfectly linear?

The meaning in #2 above is liking billiard balls not perfectly
little...one's a little higher (or to the left) then the other so when
one ball going straight hits it ...it goes upwards (or leftwards)
instead of straigth... but isn't this transversal?

Therefore isn't #2 similar to the behavior Tom Roberts wrote about the
steel bar and therefore sound would also PROPAGATE
TRANSVERSALY...threrefore isn't sound also a transversal wave
(therefore having both a longitudinal and transversal wave ....but Tom
said "no" above here......and he said above "not when it travels
through air molecules")???

Not really
Transverse waves are physically propagated due to transverse forces (i.e.
shear forces). Gases (and liquids) do not support shear forces.

If you pick up a basic textbook on seismology you'll get to a bit that
talks about S-waves and P-waves. P-waves are pressure waves, and S-waves
are 'surface waves' or 'shear waves' P-waves can be propagated through
solids, liquids or gases; S-waves can only be transmitted through solids.

The different characteristics of each allow seismologists to interpret the
received signals to model the internal structure of the earth (for
example, the outer core of the Earth is molten).

http://en.wikipedia.org/wiki/Seismology

just to clarify
P-waves are the longitudinal waves we've already discussed
S-waves are transverse waves- Hide quoted text -

- Show quoted text -

Then why is sound heard in all directions (transverse and
longitudinal) instead of only one direction (longitudinal.....since
it's a p-wave)?- Hide quoted text -

- Show quoted text -

Indeed for it's hard for you to explain why a longitudinal wave going
horizontal is heard vertically (transverse) and as if most textbooks
will happen to deal on this specific subject...

You're confusing the meaning of transverse.

In any direction in which sound is heard, the wave
which causes that sound to appear is a pressure wave,
a motion in that same direction, NOT a transverse
direction.

If I hear sound over there: ->
Then there has been a mass motion of molecules
that way: ->
Longitudinal, not transverse.

If from the same source, I also hear motion
over there:
|
|
v

It means there is a pressure wave, a bulk motion
of air molecules in that direction
|
|
v

Longitudinal, not transverse.

The reason you hear sound in all these directions
is that due to the nature of the medium, pressure
waves tend to spread in all directions. So you're
getting longitudinal pressure differences in all
those directions.

NONE OF THEM CONSITUTES A TRANSVERSE WAVE.

A transverse wave would have this characteristic:
It is propagating over here -->
But the particle motion is perpendicular, say here:
^
|

That is not the case here. Everywhere you hear sound
in air, the molecules are moving in the same axis as
the direction of propagation.

- Randy- Hide quoted text -

- Show quoted text -

Ok thks Randy

.

Relevant Pages

  • Re: New question about Longitudinal sound waves?
    ... which supports transverse waves -- air does not, ... steel bar and therefore sound would also PROPAGATE ... TRANSVERSALY...threrefore isn't sound also a transversal wave ... Transverse waves are physically propagated due to transverse forces (i.e. ...
    (sci.physics.relativity)
  • Re: Transverse speed in EM waves?
    ... >> There is no transverse velocity in an EM wave. ... the part that you're concerned with is the hump that's moving ...
    (sci.physics)
  • Re: Are Gravitational Waves Electromagnetic waves?
    ... Electric dipoles acting ... > also is transverse to the direction of the wave. ... Since an oscillating electric dipole radiates energy in all directions, ...
    (sci.physics.relativity)
  • Re: Are Gravitational Waves Electromagnetic waves?
    ... Electric dipoles acting ... >> also is transverse to the direction of the wave. ... > Since an oscillating electric dipole radiates energy in all directions, ...
    (sci.physics.relativity)
  • Re: What is the highest-frequency sound that can exist in Earths atmosphere?
    ... What is the highest-frequency sound that can exist in Earth's ... air can be approximated as a continuous fluid. ... breaks down when the wavelength of the wave becomes comparable with the ... mean free path of the molecules that make up the atmosphere. ...
    (sci.physics.research)