Tuesday, 17 August 2010

Organ installation continues

John Budgen continues to install the Little Hampden Church Organ – interrupted periodically by visitors. I heard it played this afternoon – not all the pipes were installed but it sounded good to me.

Here are some more pictures of the organ arriving and being installed.

John and I have been having interesting discussions about organ pipes: I can remember some of the basic physics, but not the equations. The sound is made by a standing wave within the pipe which depends on the length of the pipe between the mouth (the slit at the bottom) and the end. Some of the pipes are open-ended (the metal ones n our organ) and some have plugs at the end so are closed (the wooden ones). The closed pipes resonate at half the frequency (one octave lower) than an open pipe of the same length. Also, according to Wikipedia, an open pipe produces odd- and even-numbered harmonics whereas a closed or stopped pipe produces only odd-numbered harmonics.

The pipes are tuned by slightly altering their length. You can see the sleeves on the metal pipes in the picture below. Sliding these up and down change the length – and so the pitch – slightly. The stopped wooden pipes have a movable stopper which can lengthen or shorten the resonant chamber thus altering the pitch. We did discuss how the different tones are made – but this got beyond my physics.

1 comment:

rosie said...

Can't wait to see it and hear it!