] [Thread Prev
AW: AW: Underwater latency (not completely OT) ;-)
The way sound travels in different phases (solid, liquid, gaseous) is
actually rather different on a half-macroscopic scale (i.e. while the laws
how atoms and subatomic particles interact are believed to be the same and
the equations for speed of sound calculated from density and
compressibility (or rather its different definitions) look the same, the
process or how it is explaind differs on the scale "in between".
If you look at the equations on a macroscopic scale, they all look like c
= SQRT(K/rho) with K a constant (actually a 2nd order tensor, a modulus).
In the case of gases, K= chi*p with chi the isentropic exponent (a
constant) and p the pressure. Substituting with the definition of the
density in gases, rho = p/RT (R the Reynolds number, T the Kelvin
temperature), we get c=SQRT(chi*R*T), and voilá - the speed of sound in
air is independent from the pressure. The pitfall? This equation is only
valid up to a certain amount for the avg. free length of path (don't
remember how this was defined - I came from the condensed matter area).
Thinking about it, I don't see the logical explanation that sound travels
faster in water than in air. There are different mechanisms involved. And
if we'd breathe argon and bathe in quicksilver, things would be different
Elasticity is not the same as compressibility. The short explanation:
elasticity describes changes if you apply force in one direction (like
pulling on a string), while compressibility is if you push from all sides
Von: Doug Cox [mailto:firstname.lastname@example.org]
Gesendet: Dienstag, 15. März 2005 22:17
Betreff: Re: AW: Underwater latency (not completely OT) ;-)
This can be found here: http://hypertextbook.com/facts/2000/NickyDu.shtml
Sound is a type of longitudinal, mechanical wave. They need a medium to
propagate and will not travel through a vacuum. Sound travels at
different speed in different media. The speed of sound is determined by
the density and compressibility of the medium. Density is the amount of
material in a given volume, and compressibility is the how compacted
could a substance become for a given pressure. The denser and the lower
the compressibility, the slower the sound waves would travel. Therefore,
the speed of sound is about four times faster in water than in air. The
speed of sound can also be affected by temperature. Sound waves tend to
travel faster at higher temperatures. I have found different values for
the speed of sound in water in different sources. They range from 1450
to 1498 meters per second (m/s) in distilled water and 1531 m/s in sea
water at room temperatures (20 to 25 °C).
The speed of sound in a medium can be determined by the equation...
/v/ = (/B//ρ)^1/2
/v/ is the speed of sound,
/B/ is the bulk modulus of elasticity, and
ρ (rho) is the density.
The bulk modulus of elasticity, also known as the compressibility, is
the relationship between pressure and volume. It is a measure of how
much an increase in pressure would decrease the volume.
Nicky Du -- 2000
Jesse Lucas wrote:
> Rainer Thelonius Balthasar Straschill wrote:
>> If I remember my (very) basic university classes in physics, we
>> usually would test any theories we might have by bringing them to
>> extreme values and see what happens. If lower density = lower speed
>> of sound, then we would have sound travelling at infinite speed in
>> vacuum. I don't believe this is the case.
> In space there is no medium for sound to travel through. See the tag
> line to the film "Alien."