Soundwaves Boost Wing Lift

On Sun, 21 Aug 2005 19:22:47 -0700, Chad Irby wrote
(in article ):

Kinda makes you wonder if they used a particular kind of "noisy" sound
wave, or simple shapes like sine waves.

It'd be really funny if it turned out to work with random or
less-patterned noise, and they missed it because they were too
organized...

One would be tempted to think this, but all noise (including triangle and
square waves) can be constructed from a sum of sines and cosines. It is
called Fourier's Theorem, and it works so well nearly all digital signal
processing is based on it to some extent. Note that the researcher's 400 Hz
signal (close to the A flat above middle C) could form some pretty irritating
beats with the engine/propeller. Concert A is 440 and I suspect anybody who
has worked with military aviation is familiar with the sound of the 400 Hz
power systems.

-- Charlie Springer

In article l.net,
Charlie Springer wrote:

On Sun, 21 Aug 2005 19:22:47 -0700, Chad Irby wrote
(in article ):

Kinda makes you wonder if they used a particular kind of "noisy" sound
wave, or simple shapes like sine waves.

It'd be really funny if it turned out to work with random or
less-patterned noise, and they missed it because they were too
organized...

One would be tempted to think this, but all noise (including triangle and
square waves) can be constructed from a sum of sines and cosines.

Technically, yes, but there could be too many situations where "simple"
noise has nothing like the same effect "complex" noise does.

Considering that the airflow across the wings of small aircraft is
generally subsonic, simple versus complex waveforms could make a real
difference (for the generation or prevention of standing waves?).

--
I don't have a lifestyle.
I have a lifeCSS.

On Sun, 21 Aug 2005 22:55:17 -0700, Chad Irby wrote
(in article ):

One would be tempted to think this, but all noise (including triangle and
square waves) can be constructed from a sum of sines and cosines.

Technically, yes, but there could be too many situations where "simple"
noise has nothing like the same effect "complex" noise does.

Considering that the airflow across the wings of small aircraft is
generally subsonic, simple versus complex waveforms could make a real
difference (for the generation or prevention of standing waves?).


Yet the researchers say they used 400 Hz sinusoidal signals and make no
mention of phase adjustments or feedback compensation to null out situations
that would cause detachment.

As for "technically, yes" I would say "and physically". Water waves are a
good example. The bow or stern wave from a boat is not a sinusoid. But there
is dispersion in water surface waves based on wavelength, so sinusoidal
components that can be added together to get the original shape, separate
over time till you see the longest waves leading and the shortest bringing up
the rear. You get a chance to see the "Fourier components" that make up the
original wave, and with no special equipment.

-- Charlie Springer