Yes it does make all the difference. You have consistently insisted that an open pipe end can't reflect the wave back down the pipe (with inverted phase in the pressure domain). Clearly it can and does and that's the whole basis of how TLs really work.
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Everyone needs to get over this... I'm sorry that I personally feel an explaination of background in a topic should be necessary when the person in question is looking down his nose of those with proven knowledge and/or credentials. As this thread has grown, many more have come to the realization that villastrangiato is reluctant to produce physical proof of his beliefs. So maybe I was just a little ahead of the curve when I questioned his background. In lieu of that physical proof, I personally would accept villastrangiato's theories as a constructive counterpoint to the proven status quo, if he did disclose his experience on the topic, (whatever that may be), and prove he was more than just an arm chair acoustic quarterback. ...with crazy cut'n'paste skills. Debating a topic/theory is one thing. If however you're going to say authorities on a subject are wrong, you need to back it up with something.
If everyone else feels it's irrelavant fine, but i don't care. As with many topics, I'm a complete newb in the world of TL theory, and I perfer to substantiate the sources of information at my disposal. The forementioned Wikipedia is a glaring example of how to be mislead when trying to obtain accurate direction.
So considering the likelyhood of witnessing any physical proof is small. The next best thing IMHO to substantiate counter theories to the accepted practice is proof that the topic at hand is being argued by someone with experience. Which is obviously why I asked...
I concluded very early on (as many others now have) that this thread has only entertainment value.
/defence of opinion
Threads like this have real value: they can motivate you to read and learn, if for no other reason but to prove someone else wrong.
My issue is with making this personal, using intimidation and belittling taunts. Calling him a troll doesn't add to the conversation, knowing his real name is not important and neither is his level of education. Anyone should be allowed to talk on any subject without being bullied, regardless of how outlandish his ideas are.
My issue is with making this personal, using intimidation and belittling taunts. Calling him a troll doesn't add to the conversation, knowing his real name is not important and neither is his level of education. Anyone should be allowed to talk on any subject without being bullied, regardless of how outlandish his ideas are.
And that somehow proves that waves can't reflect back up a tube? Discontinuities reflect waves was all I was mentioning, go sit in a bathtub and watch what happens when the wave hits the side of the tub! Not rocket science, here. Resonances happen in pipes of all kinds.
Maybe I'm missing what you are trying to argue, though? This is a very weird thread, starting off with an agressive question and then going downhill from there...
Are you trying to suggest that wave behavior in shallow pools of water predicts acoustic behavior?
If so, maybe you should take a trip out to Meyer Sound Lab in Berkley, California so you can tell them how wrong they are here:
"Unlike shallow water waves, which are non-linear and can combine to form new waves, sound waves at the pressures common in sound reinforcement cannot join together: rather, they pass through one another linearly. Even at the high levels present in the throat of compression drivers, sound waves conform to linear theory and pass through one another transparently. Even at pressure levels of 130 dB nonlinear distortion is less than 1%."
Which is quoted on their public website here:
Can Line Arrays Form Cylindrical Waves? A Line Array Theory Q & A
Hi Bill
I gave up at about page two.
Like AJin FLA, the high point for me was when the guy changed the Wikipedia page! That was a classic. I will never forget that trick. And just as AJ said, I only wish he could have used it as support. I would have died laughing at that one.
A couple of times I have been caught by people who play the audiophool dogma to the hilt, but faceasciuosly (SP?). They go on and on arguing senslesly to see how long I will take them serious. Its amazing how long people will go on arguing the absurd with someone.
I gave up at about page two.
Like AJin FLA, the high point for me was when the guy changed the Wikipedia page! That was a classic. I will never forget that trick. And just as AJ said, I only wish he could have used it as support. I would have died laughing at that one.
A couple of times I have been caught by people who play the audiophool dogma to the hilt, but faceasciuosly (SP?). They go on and on arguing senslesly to see how long I will take them serious. Its amazing how long people will go on arguing the absurd with someone.
I have to say that experts in general cling to what they already know, and understand
True scientist are openminded to what they dont understand
Thats the nature of science
And it often starts with nothing else but curiosity
To change the wikipedia, thats close to work of art, or an artist worthy
Like placing a popo in a tin can
Food fore thoughts I would say, and a bit scary too
It means that we believe what they tell us to believe
True scientist are openminded to what they dont understand
Thats the nature of science
And it often starts with nothing else but curiosity
To change the wikipedia, thats close to work of art, or an artist worthy
Like placing a popo in a tin can
Food fore thoughts I would say, and a bit scary too
It means that we believe what they tell us to believe
lol facetiously
i think its humourous that so many folks are getting vexed at some guys and his own personal opinions.
I, myself, have argued, maybe too long and too aggressively against theories i believe are hocus, or maybe just not telling everything there is to consider. This has in some cases, esp with P10 (to my shame tbh) gone a wee bit too far.
True or not. established theory or not. proven or not.
It doesnt matter.
an example of my opinion:
MY OPINION:
Air IS non linear. very very slightly. It is assumed to be linear as the non linearity is so small. In cases like this the factor would be ignored in order to simplify calcs. this introduces errors and ther IS a margin for another model to become more accurate. the analogy of TL to an electrical circuit is just that: an analogy. its not perfect, the whole story, or the definitive answer.
But it is the best theory we have ATM.
Some people will take that statement to heart, be offended and tell me im wrong.
However, i may be wrong, but i may also be exactly right. Unless another model is devised which supercedes the present ideas, popular science will say im wrong. And im happy with that.
The whole point is, this debate and difference of ideas is nedded to move the science forward, and no theory is devised and proven, without first being thought of, ridiculed, dissected...and then eventually proven. even after all that people will pick at it (like i just did)
a little hint though folks....
testosterone does not accelerate the scientific process of discovery.
so chill your beans and accept that everyone has a right to an opinion, religion, whatever; however misguided it may be. aggressive retaliation from either party is just plain stupid, and stupid doesnt prove any theories😀
Villastrangiato,
You seem to be quite adament that a change in propagation medium density is the sole boundary condition to allow for acoustic wave reflections.
"The only way you can get a reflection of a sound pressure wave is with a substantial shift in density."
Do you stand by this assertion?
-David
You seem to be quite adament that a change in propagation medium density is the sole boundary condition to allow for acoustic wave reflections.
"The only way you can get a reflection of a sound pressure wave is with a substantial shift in density."
Do you stand by this assertion?
-David
I have to correct my idiot self. It is the odd harmonics that define the standing waves of a quarter wave resonator:
Standing Waves and Wind Instruments
and
PhysicsLAB: Resonance in Pipes
This seems to be a contradiction. It may be true in some cases, but lets hope that they are the exception. A true expert IS also a true scientist. Otherwsie he is not really an expert, but a charlatan.
"It's going the other way" ?
LOL!!! And where would that be in a pipe closed off at one end by a loudspeaker?
Here's another version of what defines a standing wave
"A standing wave, also known as a stationary wave, is a wave that remains in a constant position. This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite directions. In the second case, for waves of equal amplitude traveling in opposing directions, there is on average no net propagation of energy.
Standing waves in resonators are one cause of the phenomenon called resonance."
It can be found here:
Standing wave - Wikipedia, the free encyclopedia
If you read further, you will find the following:
As an example of the second type, a standing wave in a transmission line is a wave in which the distribution of current, voltage, or field strength is formed by the superposition of two waves of the same frequency propagating in opposite directions.
It's obvious to me that certain individuals on this site who have been commenting on this thread and who have contributed to other Wiki pages that seek to define Acoustic Transmission Lines - are attempting to equate the phenomena associated with electromagnetic field propagation through media with the phenomena associated with acoustic (mechanical) wave propagation. They are in fact not equivalent and the reference I've provided to the Meyer Sound link establishes physical proof that sound waves don't reflect off of one another. Behavior of air pulses in a confined space such as a smooth walled pipe is a special case. The confinement of the air column is not all that different from the confinement of gas bubbles surrounded by a higher density medium such as water in the cavitation case I cited earlier. Reflection of any sound wave requires a substantial change in density - such as a hard surface or change of media. Trying to equate acoustical impedance of air vibrating in a pipe with the electrical impedance for electromagnetic radiation in an RF waveguide is a fools game. They both must obey the laws of physics - conservation of mass and energy - but that's where the useful comparison ends.
I read this before. Its simply not true. Reflections can occur without a change in density, but by a simple change in the boundary for example, such as an open end of a pipe, or the edge of an enclosure. There is no density change only an impedance change.
boundary change/acoustic impedance reflects the pressure wave? am i correct in my understanding? if i am, then surely this is a product of the (relativley) smaller mass of air in the tube, contacting the larger mass of air in the room?
this is my understanding of what you say, although whether im right in that assertion i dont know lol, and im aware its more complex than just this.
also if i may say, i THINK (i dont presume to know) im right in saying...
the refraction of a sound pressure wave is due to density of media, NOT the reflection....
villastrangiato;2107643seek to define [B said:
yes they do equal electrical theory to acoustic behavior. rather clever really. i think that since air is NOT water, although fluid, the analogy is rather good. after all i have never heard of electric fields influencing eachother as surface water ripples do either....
maybe the analogy of SURFACE water ripples is a bad one....deep water waves may be closer to air methinks
If you read even further, you find:
"Another example is standing waves in the open ocean formed by waves with the same wave period moving in opposite directions."
and:
"Standing waves are also observed in physical media such as strings and columns of air."
and:
"Standing waves are also observed in optical media such as optical wave guides, optical cavities, etc."
LOL yes...... every time my washing machine spins, the wooden floor resonates sympathetically and the water in the basin forms standing waves, with interferance patterns...forming a stationary opposing arcs of peaks....looks a bit like something youd make in meringue
Mass is not density. There can ve two volumes with the same denisty and different masses. But total mass has nothing to do with the reflection. The wave has no idea how much mass the room has or the tube. It "sees" a change in the boundary in its local vicinity and it adjusts itself to that change. This creates reflection and diffraction in various amounts depending on the particulars.
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