| Topic: |
Science > Physics |
| User: |
"Anonymous" |
| Date: |
09 Jan 2005 09:10:59 PM |
| Object: |
Underwater finger snap |
I originally posted this to alt.sci.physics.acoustics
but there isn't much activity there. I am reposting to
sci.physics.
I'm not near a pool or anyplace else to do the obvious simple
experiment, but I'm hoping someone here can help. This
is from a scene in a movie and it seemed physically wrong:
Some divers are underwater, completely submerged, about 3 to
6 meters apart. One of them snaps his fingers and the movie
audio is a normal (in air) crisp sounding "SNAP!".
Wouldn't the water dampen the initial snap of the finger
against the palm of the hand? (Maybe a really strong snap
wouldn't be dampened too much.)
Wouldn't the sound wave from the snap be dampened by the water?
Wouldn't the listener's total "acoustic mechanism" (ears, head,
sinus cavities, etc.) be dampened while submerged in water?
Wouldn't the "SNAP!" be heard as more of a "plunk"?
Does the answer depend on the size of the body of water (bath
tub, swimming pool, ocean) maybe due to echoes off the sides of
the tub or pool but not the ocean?
Because it's a movie, the audio is presumably supposed to be as
much the ears of the observer as the camera is the eye of the
observer. So, while the camera is focused eye to eye with the
finger snapping diver:
If we use a standard underwater microphone (whale or dolphin
recordings) on the camera instead of a person's ears to monitor
the finger snap, would the microphone record a crisp "SNAP!" or a
muffled "plunk"? I still think it would be a plunk, not a "SNAP!"
Thank you.
.
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| User: "The Ghost In The Machine" |
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| Title: Re: Underwater finger snap |
09 Jan 2005 11:01:34 PM |
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In sci.physics, Anonymous
<Use-Author-Supplied-Address@[127.1]>
wrote
on 10 Jan 2005 03:10:59 -0000
<KJE3ZGGO38361.8826273148@anonymous.poster>:
I originally posted this to alt.sci.physics.acoustics
but there isn't much activity there. I am reposting to
sci.physics.
I'm not near a pool or anyplace else to do the obvious simple
experiment, but I'm hoping someone here can help. This
is from a scene in a movie and it seemed physically wrong:
Some divers are underwater, completely submerged, about 3 to
6 meters apart. One of them snaps his fingers and the movie
audio is a normal (in air) crisp sounding "SNAP!".
Wouldn't the water dampen the initial snap of the finger
against the palm of the hand? (Maybe a really strong snap
wouldn't be dampened too much.)
Try putting your hand into a bowl of water and snapping your
fingers. It should at least answer some of your questions. :-)
I've noticed that my fingers don't snap as well dry as when
they are wet. However, that's in air.
Wouldn't the sound wave from the snap be dampened by the water?
No, water conducts sound quite well, when the sound isn't
bent away by a thermocline. (Read _The Hunt For Red October_
for examples of how submarines can use variances in water
temperature and salinity to hide.)
Wouldn't the listener's total "acoustic mechanism" (ears, head,
sinus cavities, etc.) be dampened while submerged in water?
Wouldn't the "SNAP!" be heard as more of a "plunk"?
It may very well be, admittedly. One problem with microphones
is that they're not ears -- an example is how one properly
records the howling of the wind during a tornado, for instance.
I suspect water miking has some issues there, too.
Does the answer depend on the size of the body of water (bath
tub, swimming pool, ocean) maybe due to echoes off the sides of
the tub or pool but not the ocean?
Because it's a movie, the audio is presumably supposed to be as
much the ears of the observer as the camera is the eye of the
observer. So, while the camera is focused eye to eye with the
finger snapping diver:
If we use a standard underwater microphone (whale or dolphin
recordings) on the camera instead of a person's ears to monitor
the finger snap, would the microphone record a crisp "SNAP!" or a
muffled "plunk"? I still think it would be a plunk, not a "SNAP!"
Hard to say without testing it. I don't have an underwater
mike handy. :-)
Thank you.
--
#191,
It's still legal to go .sigless.
.
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| User: "Italy Anonymous Remailer" |
|
| Title: Re: Underwater finger snap |
11 Jan 2005 10:02:14 AM |
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Wouldn't the water dampen the initial snap of the finger
against the palm of the hand? (Maybe a really strong snap
wouldn't be dampened too much.)
Try putting your hand into a bowl of water and snapping your
fingers. It should at least answer some of your questions. :-)
But with my head out of water, my ears and head not being dampened.
Swimming underwater, it seems that everything is sort of muffled.
The sound of objects hitting together (say, against the side or bottom
of a boat) is much different when the detectors (ears) were beneath
the surface than in air.
In air, everyday sounds (fingers snapping) are primarily detected by
air mediated contact with the ear drum. Underwater, is the entire
head acting as a detector? Are sounds heard by means other than just
waves impinging on the outer part of the ear drum but by water borne
waves enveloping the whole head? Maybe that's why it sounds muffled?
Or do I hear things differently than others?
Wouldn't the sound wave from the snap be dampened by the water?
No, water conducts sound quite well, when the sound isn't
bent away by a thermocline.
Even though well conducted, wouldn't it alter the nature of the sound
(SNAP to muffled snap) compared to conduction in air? Maybe the
muffling occurs in the ear itself? Hence the need to distinguish
between a microphone or other non-ear detector and a real anatomical
ear?
Thanks!
.
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