Recording water waves

I wonder if anyone know of any previous attempts at recording the
shape of water waves as a sound source. This is what i had in mind:

When one looks across a water surface, you often see a delicate and
complex interaction of waves that would be ideal to transfer directly
into sound, however it is physically impossible to capture one
"moment" of each point of an entire surface, in a straight line from
one point to each other.

But the same effect could be gotten by somehow measuring ONE STATIC
POINT on the surface over time, as waves pass by it and thus expose
their entire shape to the one point measured by some sort of
electronics. The ideal way to achieve this would be through some sort
of laser light with measured reflection, somewhat similar to a CD
player, placed below the surface and avoiding to disturb the natural
motions of the surface in any way.

I really would not recommend using some kind of moving floater, as
they interfere with the waves too much and also don't follow them
entirely-though this could of course be used intentionally. The same
with using a vertical transparent screen with some sort of optical
measuring, as water crashing against the wall would have a particular
behaviour that would usually not be sought after.

The result, of course, would be a complex harmony or intermodulation
of very slow motions ranging from 0.1 to about 4 or 5 hertz, plus
overtones. Very small streams and vibrations in small buckets etc.
could possibly be up to 20 hertz in fundamental frequency.

This would simply be sped up about 20 to 1000 times to be fully
audible. Of course this also means that the time is very compressed,
but that is part of the whole idea.

There would be great differences from placing the "measurement" at
different points, and closer to the edge of the body of water used. It
would be of great interest to run several recorders at different spots
in parallel at the same time, to compare how they respond to the events.

The whole point is that there is very unique and varied responses to
the water by the change of winds over time, and possibly very few
other interferences such as having a large floating bridge nearby
which would probably produce a nearly fixed-pitch sine wave.

There is also potential for using non-natural bodies of water-barrels,
buckets or bathtubs, to pick up wind in a different way. The motions
of rivers and streams could of course also be recorded, though they
would be a lot more regular than a "still" body activated only by wind.

And walls and floating objects nearby could also be placed to act as
intentional "filters" for diferent frequencies, also draining channels
into-or from-the body of water recorded would be permanent, probably
noise-like sound sources.

Of course other objects, light enough to move in the wind, could be
"motion recorded" in the same way. But they have very strong and fixed
resonant frequencies which makes them less interesting, as they are
more like instruments activated by wind. A water surface is peculiar
because it has no fixed resonant frequencies at all, the shape and
speed of the waves is only created by the wind itself. Thus it will be
much more complex and varied.

What i wonder now is if there is any history of this kind of "surface
motion recording" being done or attempted before.

At 09:35 AM 9/1/2005, you wrote:
>I wonder if anyone know of any previous attempts at recording the
>shape of water waves as a sound source. This is what i had in mind:
>
>When one looks across a water surface, you often see a delicate and
>complex interaction of waves that would be ideal to transfer directly
>into sound,
//
>What i wonder now is if there is any history of this kind of "surface
>motion recording" being done or attempted before.

Sounds like a nice idea for a performance art piece... participants
could toss ball bearings in a pool and watch ripples travel to the
sampled point(s), which could be indicated by (a) visible laser(s)
perpendicular to the water's surface. Plurals there would be a
version with harmony. It could be a round pool in a round room with
speakers placed in the room in a congruent fashion to the placement
of the sampled points in the pool...

-Carl

Two overhead cameras, or one with known light source which can map out
peaks and troughs by color. Instantaneous point datas will reflect
elevation, slope and direction, might take the same processing to
resolve as to do a whole surface stereoscopically, then to pick out
point or points.

Clark

First search result for "video stereoscopy":

http://cgrg.geog.uvic.ca/abstracts/EaketUseThis.html

Eaket, J., F. Hicks and A. Peterson, A.E. Use of stereoscopy for dam
break flow measurement. Journal of Hydraulic Engineering, 131(1) p.24-
29. 2005

"This investigation explored the applicability of video stereoscopy
for the measurement of unsteady open channel flows. Specifically, the
three-dimensional water surface profile and flow velocities associated
with scale model dam break events were considered. Stereo images of
the unsteady flow event were obtained using three, time-synchronized,
video cameras situated above the tank such that, at all times, the
area of interest was captured by at least two of the three cameras. To
establish a point of reference from image to image, floating plastic
tracking particles were placed on the water surface. The three-
dimensional coordinates of the particles were then calculated using
the camera positions and the locations of the individual plastic
particles in the stereo images. Particle velocities were also deduced
from the analysis of consecutive images. Based on this preliminary
investigation we conclude that video stereoscopy is a promising method
for measuring highly dynamic flows."

I'm dubious that this is the best approach. Note...

"To establish a point of reference from image to image, floating
plastic tracking particles were placed on the water surface."

After thinking about a diffraction-based laser system, I think an
easy and possibly-sufficient method would be to build a very weak,
lightweight pickup, mount it in a small tube fastened and
perpendicular to the floor of the pool, and have a styrofoam
cylinder floating in the tube. The pickup could be located in
the bottom of the tube where it will be far from changes in the
water's level, while the top of the tube is slotted to allow water
to pass through freely (in fact the top of the tube could simply
be three pieces of coat-hanger wire).

-Carl

>Two overhead cameras, or one with known light source which can map out
>peaks and troughs by color. Instantaneous point datas will reflect
>elevation, slope and direction, might take the same processing to
>resolve as to do a whole surface stereoscopically, then to pick out
>point or points.
>
>Clark
>
>First search result for "video stereoscopy":
>
>http://cgrg.geog.uvic.ca/abstracts/EaketUseThis.html
>
>Eaket, J., F. Hicks and A. Peterson, A.E. Use of stereoscopy for dam
>break flow measurement. Journal of Hydraulic Engineering, 131(1) p.24-
>29. 2005
>
>"This investigation explored the applicability of video stereoscopy
>for the measurement of unsteady open channel flows. Specifically, the
>three-dimensional water surface profile and flow velocities associated
>with scale model dam break events were considered. Stereo images of
>the unsteady flow event were obtained using three, time-synchronized,
>video cameras situated above the tank such that, at all times, the
>area of interest was captured by at least two of the three cameras. To
>establish a point of reference from image to image, floating plastic
>tracking particles were placed on the water surface. The three-
>dimensional coordinates of the particles were then calculated using
>the camera positions and the locations of the individual plastic
>particles in the stereo images. Particle velocities were also deduced
>from the analysis of consecutive images. Based on this preliminary
>investigation we conclude that video stereoscopy is a promising method
>for measuring highly dynamic flows."

> "To establish a point of reference from image to image, floating
> plastic tracking particles were placed on the water surface."

They are interested in flow not surface shape. The way I thought it is
like holographic interferometry but in time domain too.

Clark

>> "To establish a point of reference from image to image, floating
>> plastic tracking particles were placed on the water surface."
>
>They are interested in flow not surface shape. The way I thought it is
>like holographic interferometry but in time domain too.

Hmm... -Carl