# Fundamental frequency question

I do not understand what is meant in this question:

An open organ pipe has a fundamental frequency of 430 Hz. A closed organ pipe has a fundamental frequency that is the second harmonic of the open organ pipe. What are the lengths of the two pipes?

Does the bolded part mean that the fundamental frequency of the closed pipe is twice that of the open pipe? (since 2*fundamental frequency = second harmonic frequency) Something about the wording is tripping me up here.

If so, how would I find the length only knowing frequencies (not velocities or wavelengths)?

thanks!

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Hootenanny
Staff Emeritus
Gold Member
Try plotting pressure changes along the length of the pipe. The highest pressure will be at the closed end of a pipe (anti node) and the lowest pressure will be at the open end of the pipe (node). This may help you determine the wavelength of the fundemental frequency.

HINT: The wavelengths will be fractional

Regards,
-Hoot

Doc Al
Mentor
kellyneedshelp said:
Does the bolded part mean that the fundamental frequency of the closed pipe is twice that of the open pipe?
That is correct.

If so, how would I find the length only knowing frequencies (not velocities or wavelengths)?
You can't. But you should know the speed of sound. (Look it up!)