# Sound waves in organ pipes.

The topic came up the other day in class, about how the wave frequencies vary in each pipe of an organ. I am looking for some comprehensive information on the topic, and it would be great if someone could direct me, or maybe help a little bit as I am not so sure, as we haven't covered the topic yet, but a head start is always nice. Thanks =]

From what I know now, I would have thought that the higher pitches would have a shorter wave frequency, than deeper ones.

Danger
Gold Member
Well... you're a busy little bugger, aren't you? Questions everywhere...

As a rule, pitch increases with the length, and inversely to the diameter, of the resonating cavity (pipe, in this case). There are factors such as air speed, valving, etc. that can change that significantly, though. I'm leaving off to make way for an expert here.

^ Cheers Danger for some help, yeh well I've just sat a physics exam in the past week and got a shock, and really in a subject that I enjoy so much, to be achieving so average, I really want to work at it, and th ebest way is to talk to the people who know what they're on about =] !

No, pitch varies inversely with length. For air in a pipe the width only has a small effect.

Pitch is directly related to the frequency, which is inversely proportional to the wavelength.
The wavelength is directly proportional to the length.

Long pipe = long wavelength = low frequency = low pitch
Short pipe = short wavelength = high frequency = high pitch

Thank you, is there any more you could tell me on the subject? I'm geussing that is really just the basics, and I am looking to maybe go into a bit more detal. Thanks.

FredGarvin
What is the relationship between energy and pitch? For example does more energy need to be passed through the pipe for a higher noise? Or is that speed?

The pitch of an organ pipe is due to the resonant frequency of the air column. Pressure changes due to how hard the pipe is blown on have only a slight effect on frequency. What does change how a pipe should be tuned is the medium it is played with.

Air has a different resonant frequency than steam in the same pipe. So a steam caliope is tuned differently than an organ played with air because the difference in density of the steam changes the resonant frequency of the air column. You also have to tune an organ differently for major changes in altitude. The thinner air at high altitude will give a higher pitch than the thicker air at sea level.

The length of the pipe controls pitch and the diameter increases the volume of air which gives a louder soundfrom a large diameter pipe than a small diameter pipe pipe. You also have to increase the diameter of a lower pitch pipe to maintain the same loudness since the higher pitch pipe will have more actual energy in the sound than a lower pitch pipe.

Below is a link to a site that will explain some of it to you. Chapter five covers open and closed air columns.

http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/soundtoc.html [Broken]

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