Listening to some music, I observe that most of the drumbeat sounds 
appear to be in the region below 200 Hz.

Wolfram Alpha tells me [EVENTUALLY!] that a 200 Hz sound has a 
wavelength of about 170 cm.

Question: Since the doorway to be bedroom is less than 170 cm wide, does 
that mean those waves can't leave the room? Or does the fact that it's 
more than 170 cm tall negate that?

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Orchid XP v8 <voi### [at] devnull> wrote:
> Listening to some music, I observe that most of the drumbeat sounds 
> appear to be in the region below 200 Hz.

> Wolfram Alpha tells me [EVENTUALLY!] that a 200 Hz sound has a 
> wavelength of about 170 cm.

> Question: Since the doorway to be bedroom is less than 170 cm wide, does 
> that mean those waves can't leave the room? Or does the fact that it's 
> more than 170 cm tall negate that?

  I think you have a misconception of what wavelength means. The misconception
probably comes from those 2D drawings of wave functions.

  A sound wave (nor an electromagnetic wave for that matter) is not some
kind of sine wave which goes through the air. The sine wave function you
see drawn on a picture is just the representation of the function which
tells which direction the wave is "pushing" at certain point (and how
"strongly" it's "pusing"). The sine wave drawing is just a graph which maps
time to amplitude ("strength" of the sound wave), it's in no way meant to
represent the *physical* appearance of a sound wave.

  A sound wave is simply a phenomenon of air molecules pushing (and pulling)
adjacent air molecules. The phenomenon traverses through air. The maximum
strength at which this "pushing" happens is the amplitude of the wave, and
the rate of change between "pushing" and "pulling" is the frequency. The
distance between two "pushing" peaks is the wavelength.

-- 
                                                          - Warp

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Orchid XP v8 <voi### [at] devnull> wrote:
> Listening to some music, I observe that most of the drumbeat sounds
> appear to be in the region below 200 Hz.
>
> Wolfram Alpha tells me [EVENTUALLY!] that a 200 Hz sound has a
> wavelength of about 170 cm.
>
> Question: Since the doorway to be bedroom is less than 170 cm wide, does
> that mean those waves can't leave the room? Or does the fact that it's
> more than 170 cm tall negate that?

Neither. It just means that the sound will spread very uniformly in the bedroom:

http://en.wikipedia.org/wiki/Diffraction#Single-slit_diffraction

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"Orchid XP v8" <voi### [at] devnull> wrote in message
news:4a74431c$1@news.povray.org...

> Question: Since the doorway to be bedroom is less than 170 cm wide, does
> that mean those waves can't leave the room? Or does the fact that it's
> more than 170 cm tall negate that?

Sound (pressure) waves are longitudunal. You are thinking electromagnetic
waves, which are transverse.

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somebody <x### [at] ycom> wrote:
> You are thinking electromagnetic waves, which are transverse.

  A photon will travel rectilinearly, not in a sine wave pattern.

-- 
                                                          - Warp

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"Warp" <war### [at] tagpovrayorg> wrote in message
news:4a747a87@news.povray.org...
> somebody <x### [at] ycom> wrote:
> > You are thinking electromagnetic waves, which are transverse.
>
>   A photon will travel rectilinearly, not in a sine wave pattern.

Transverse waves doesn't mean that the particle (or force carrier) travels
sinusoidally. In EM waves, field disturbances (E and B) are perpendicular
(mutually and) to the direction of motion. This is all the way back from
classical EM. Photons come in play with QFT with wave/particle duality, but
that still doesn't make EM waves longitudunal. Further, you cannot pinpoint
a photon's trajectory if you precisely know its wavelength (HUP), which of
course doesn't mean photons follow a sinusoidal path, but it makes the
transition from classical to quantum somewhat more intuitive, I think. A
wave packet (short duration in relation to wavelength) with high enough
energy will look just like a classical particle zipping by, but such
characterizations are scale dependent. With everyday EM signals, we are
mostly dealing in the wave realm.

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Orchid XP v8 wrote:
> Question: Since the doorway to be bedroom is less than 170 cm wide, does 
> that mean those waves can't leave the room? 

Sound waves are longitudinal.
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/sound/u11l1b.html
Hence, they'll fit thru any hole big enough to not diffract the wave as it 
goes through the hole.

Light is (essentially) a traverse wave[1], which is why your microwave oven 
has little holes in the screen so you can see in without getting fried. It's 
working like you think - the light has a frequency high enough that it fits 
thru the holes, while the microwaves are bigger and bounce off.

On the other hand, radio waves are *so* big they go thru lots of inter-atom 
holes at once (like a wave going past a row of pylons holding up a pier) and 
hence will go thru walls where visible light won't.

[1] Of course, it's not a wave, but the math makes it have many of the same 
properties as a wave, and this is one of them. That's why polarizers work 
such as in sun-glasses. You can't polarize a longitudinal wave.

-- 
   Darren New, San Diego CA, USA (PST)
   "We'd like you to back-port all the changes in 2.0
    back to version 1.0."
   "We've done that already. We call it 2.0."

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Darren New <dne### [at] sanrrcom> wrote:
> On the other hand, radio waves are *so* big they go thru lots of inter-atom 
> holes at once (like a wave going past a row of pylons holding up a pier) and 
> hence will go thru walls where visible light won't.

  I don't think it's as simple as the wavelength determining how well
electromagnetic radiation can traverse through matter. For example, x-rays
have a shorter wavelength than visible light, yet x-rays have more penetration
through matter.

-- 
                                                          - Warp

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Warp wrote:
> somebody <x### [at] ycom> wrote:
>> You are thinking electromagnetic waves, which are transverse.
> 
>   A photon will travel rectilinearly, not in a sine wave pattern.

But the math that describes the photon's interaction with nearby photons and 
electrons is based on multiplication (and addition) of complex vectors, 
which means it behaves as if there are conic-section waves involved, 
sometimes. Bascially, any given photon goes straight (until it interacts 
with something, at least), but a collection of photons will statistically 
have some properties in common with waves because of complex 
probabilities[1] involved in the interactions, which is why you get 
diffraction and such.


[1] As in, probabilities in which the probability of an event happening is a 
complex number (more specifically, a complex vector whose length is <= 1), 
and the probability of two events happening is the product of the complex 
numbers, etc.  I found it interesting that someone proved that only 
1-dimensional and 2-dimensional probabilities are consistent, and you can't 
build the same sort of system with (say) 3D vectors.

-- 
   Darren New, San Diego CA, USA (PST)
   "We'd like you to back-port all the changes in 2.0
    back to version 1.0."
   "We've done that already. We call it 2.0."

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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> On the other hand, radio waves are *so* big they go thru lots of inter-atom 
>> holes at once (like a wave going past a row of pylons holding up a pier) and 
>> hence will go thru walls where visible light won't.
> 
>   I don't think it's as simple as the wavelength determining how well
> electromagnetic radiation can traverse through matter. For example, x-rays
> have a shorter wavelength than visible light, yet x-rays have more penetration
> through matter.

I think the way it works is this:

X-rays actually are small enough to go between the atoms (altho they'll 
still interact with the electrons, which is why metal still stops them, 
having a "sea" of electrons on the surface).

Visible light hits (most) atoms and gets absorbed, reflected, etc.

Radio waves are physically bigger than the atoms (and the whole house, for 
that matter) so they basically are ghosting along like a car through air.

If you have a stiff screen with water waves going thru, waves much smaller 
than the holes will go thru, and waves much bigger than the holes will go 
thru all the holes at once and reform on the other side. Waves bigger than 
the holes but smaller than two holes will mostly bounce.

The higher the frequency, the "smaller" the photon is physically (as in, the 
more precisely you can know its position).

At least, that's the naive layman understanding I use to sound like I know 
what I'm talking about in newsgroups. ;-)

-- 
   Darren New, San Diego CA, USA (PST)
   "We'd like you to back-port all the changes in 2.0
    back to version 1.0."
   "We've done that already. We call it 2.0."

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