i loooove pipes :)?

Question

hey guys...i'm stuck on a physics question...can someone explain how this would be done?

two pipes of equal length are each open at one end. each has a fundamental frequency of 480Hz at 300K. In one pipe, the air temperature is increased to 305K. If the two pipes are sounded together, what beat frequency results?

thanks

Answer 1

Interesting question, but I am not sure there will be any change.

If a temperture difference of 5 degrees would make a noticable change in pitch (freq.) then pipe organs would have to be retuned every time there is a temperture change.

It seems to me, and this is only a guess, that the increse in temperture would increase the energy of the air inside, but it would also decrese the density (less molecule because of expansion).

Again, this is only a guess. . .

Answer 2

Very interesting question!

The frequency an open pipe will resonate at depends on the speed of sound. The speed of sound depends on temperature. So first, let's find the speed of sound at the slightly higher temperature. I have seen two formulas for speed of sound in air. One is an approximation: c= 0.5T + 331 or something like this, where T is the temp in degrees C and c is the speed of sound in m/s. (Your book may have the more accurate formula for calculating the speed of sound in air. If so, your prof probably imagines you'll use that one.)

Then you can calculate the frequency the pipe with the warmer air will resonate at using the formula:

f = nc/(2L) (use n=1 for the fundamental frequency)
You can also use the original temp and speed of sound to calculate the tube's length.

(If you really want to wow your prof, you could include the thermal expansion of the tube in your answer...)

Fbeat = F1-F2

Once you know the two frequencies the two pipes will resonate at, you can calculate the difference between those frequencies and this will be the answer to the question.

Answer 3

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