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## the reflection of resonance tube

What is your point? Only 19% of the power is lost, and that much must be replaced by the source if the amplitude is to be maintained.

 i mean, 81 percent is kept in the tube at the wavefront. the tube is accumulating energy even at its stable state and the peak should get higher and higher.

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 Quote by AlephZero Do you have a reference for the statement that the speed of sound changes? (which is a polite way of saying "I think that's wrong" ). What changes is the acoustic impedance of the tube, not the sound velocity. You will get partial reflection and partial transmission of energy at any change of diameter of the tube. The change to "zero diameter" at the closed end, or "infinite diameter" at the open end are just extreme limiting cases. http://www.animations.physics.unsw.e...-intensity.htm
A fair cop guv. Thanks for spotting it.
I was in two minds whether to refer to Impedance or Speed variation. I should have used impedance because that is true for narrow tubes. The effect on speed is only relevant when the tube is wide and the multiple path lengths start to be relevant to the wave speed. That would be more like 'cavities' than tubes.

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 Quote by hds123523000 i mean, 81 percent is kept in the tube at the wavefront. the tube is accumulating energy even at its stable state and the peak should get higher and higher.
A maximum level is reached when the proportion of what gets out from the end and is dissipated in the source is equal to the power input from the source. The impedance of the source is very relevant here because the "81%" can either be all reflected or all dissipated or anything in between, depending upon the match.
In the quoted case with a totally mismatched source, the maximum will be very nearly reached after about five transits of the wave. The Q factor of the resonator would be about 5.

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 Quote by sophiecentaur A fair cop guv. Thanks for spotting it.
Actually I have seen it in print once, in a book written by a the head of a very well known pipe-organ building company, in about 1900. His explanation of the difference between the actual length and effective acoustic length of a pipe was that sound travels faster in pipes with smaller diameter.
But that doesn't make sense, because a careful measurement shows that the speed in a very narrow pipe was the same as the speed in free air, but the speed reduces as the pipe diameter increased. I think Spock would call that "illogical"

 Recognitions: Science Advisor More than you probably want to know about the Q factor for resonance in pipes: http://www.fonema.se/qpipe/qpipe.htm

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 Quote by AlephZero Actually I have seen it in print once, in a book written by a the head of a very well known pipe-organ building company, in about 1900. His explanation of the difference between the actual length and effective acoustic length of a pipe was that sound travels faster in pipes with smaller diameter. But that doesn't make sense, because a careful measurement shows that the speed in a very narrow pipe was the same as the speed in free air, but the speed reduces as the pipe diameter increased. I think Spock would call that "illogical"
Not if you acknowledge the longer possible path length due to reflections off the side.
Or do you mean that you think it's illogical that a manufacturer could produce something wonderful without knowing how it works?

 Quote by AlephZero Actually I have seen it in print once, in a book written by a the head of a very well known pipe-organ building company, in about 1900. His explanation of the difference between the actual length and effective acoustic length of a pipe was that sound travels faster in pipes with smaller diameter. But that doesn't make sense, because a careful measurement shows that the speed in a very narrow pipe was the same as the speed in free air, but the speed reduces as the pipe diameter increased. I think Spock would call that "illogical"
That is interesting. Would you provide references for the book and also the measurement?

 thanks all you guys for discussion. i think i understand. the 81 percent is regarded to the total energy in the tube, not the input by the speaker. actually the 19 percent leakage equals the input. isn't it?
 Recognitions: Science Advisor Yes, that is the picture once the amplitude builds up to equilibrium.

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