As a matter of fact, I attended Georgia Tech and Southern Polytech. I am a degreed electrical engineer with Engineering Mathmatics minor. I graduated with HIGH HONORS. Electrical engineering is a specialization in physics. I worked my way from junior engineer to Sr engineer with Lockheed Martin Aeronautical Systems Co. at the F-22 and C-130 plant in Marietta Ga.Eric wrote: HAVE YOU EVER EVEN TAKEN A PHYSICS CLASS? You claim to be a PDE engineer but you seem more like an Ivar type to me.
Speed = wavelenght * frequency
Frequency = speed / wavelength
wavelenght = speed / frequency
The formulas posted above are for use in a constant medium environment for the behavior of waves and requires movement ie the term 'speed'. We have an delta speed which causes a delta wavelength of the molecular oscillations in the "traveling wave" due to the tempature environment of the medium of travel.
A "Standing wave" has properties like a wave but it is NOT a true wave, it is standing still, it has NO MOVEMENT ie no velocity, its just the net vector addition of the real waves that are moving.
Only the "traveling waves" that create the standing wave have movement down the axis of the tube, which corresponses to the appearance of a frequency change in the "standing wave".
This traveling wave is moving thru the medium which has different properties due to tempature and pressure fluxuations. The molecules traveling in the wave are the transport medium of that energy. When a molecule gains more energy, the Aplitude of its oscillation is increased, not its frequency of oscillation.
A "standing wave" only oscilates transversly from side to side setting up a vibration in the waveguide generating traveling waves towards the outside observer due to the vibration. All it is is a noise generator that is stealing energy from our cycle and turning it into sound.
FREQUENCY AT WHICH A CLOSED END PIPE WILL RESONATE ( FIRST HARMONIC) :
f (frequency of sound (Hz)) = v (
velocity of sound in air (m/s)) / 4 L (lenght of tube in meters)
We are talking about 2 different things here. You are talking about external noise generating properties. Im talking about "traveling waves" that are making up the "standing wave". The velocity term in the above equation is the velocity of the "traveling waves" that created the "standing wave". A "standing wave" by definition has NO velocity ie standing still.
Of course the "standing wave" is changing its appearance of frequency but that does not imply that the "traveling wave" is changing frequency. The same frequency travels at different wavelengths based on the medium its traveling thru. A 1 khz sound under water has a different wavelength then 1 khz sound traveling thru air of the same tempature. Its the wavelenth (distance covered per unit time ie speed) of the oscilation that is altered by a change in the medium of propogation.
Obviously. Since the wavelength (distastance per cycle) of the resonance chamber is fixed due to physical geometry it cant change and the tempature changed, the resonance frequency of the resulting "standing wave" has to change its the only variable that can change.Eric wrote:THE SPEED OF SOUND IS AFFECTED BY TEMPERATURE!!!
But conversely if there has been a frequency change in the resonance, there must have been a coresponding change in wavelength in the "traveling wave" to account for this.
There is no need to SHOUT or to be insulting obviously we misunderstood each others refrence to "frequency".Eric wrote: DID YOU GET YOUR ENGINEERING DEGREE BY MAIL? ...
We were each refering to a different frequency one of "standing wave" vs "traveling wave". Any you are applying speed to a sudo wave that is standing still.
When I think of "frequency", I think of the "traveling wave" frequency as a key component and the standing wave as just the outward observable results of what is going on below the surface.
I guess thats my EE background, we dont deal with "standing waves" very often, but we deal with alot of traveling waves. We generate the "traveling waves" to drive a system (Radio for example).
A "standing wave" is generaly the result of screwing up our power transfer. For example, a mismatch of impedance from a transmitter to the antenna can cause a "standing wave" to reflect back into the transmitter. It can also cause heating of the waveguide or burn up the trasmitter as well as a loss of transmitted power. It is generally our goal to prevent "standing waves" as a useless waste of energy.
The "traveling wave" frequency can tell us about how the waves will reflect, refract, diffract in our environment therefore it is of critical importance to understanding pulsejets and their designs.
Appearently you are just interested in the outside observable effects of the noise generation. Granted the standing wave may have its uses too. It might be giving us some clue as to what physical geometry of the tube lengths are valid for self sustaining. It just appears that most people on this board tend to totally disregard the traveling waves or not fully understand their importance.
Part of why I even brought this up is to get a chance to try to pass on that importance. I have always been a big fan of understanding WHY something works the way it does instead of memorizing formulas without understanding. In order to do that you need to know the root causes as well as the effects they have.
BTW, what is an "Ivar type"?Eric wrote: You claim to be a PDE engineer but you seem more like an Ivar type to me.