Resonators made and installed

So today I cut the resonator pipes.  These were made from 50mm diameter plastic  plumbing pipe.  Assuming a speed of sound of 344m/s in dry air at 21 degrees Celcius, I used the basic wave formula to calculate the wavelength for each note frequency - i.e.  Wavelength equals 344/frequency.

Once I knew the wavelength in metres, I was able to calculate the tube lengths.  I know that in a closed pipe resonator the air in the pipes has to be 1/4 the wavelength... In other words, the plugs stoppering the pipes should be positioned at these calculated lengths.  It doesn't actually matter what length of pipe you choose if the pipes are closed by plugs, as it's the air column we're interested in....so this allows for some aesthetic proportioning of the tube lengths to create a nice visual affect of increasingly longer pipes as you go down the octaves.

I was pleased with the way the instrument packs down.

Comments

Post a Comment

Popular posts from this blog

My first key

Here is the first key I tried to make.  At this stage I had used salt to find the nodes of the bar and had taken out wood from the underside using a small bladed saw.  However, I had cut too deeply into the wood and made the note too thin, such that it lost integrity and sounded too low to be of use on my two octave soprano. I tried a second time and got a little closer but impatience got the better of me and again I went in too deep.  I saved these early notes for experiments on staining with shoe polish (as it appears wood stain is not readily available in Shymkent either). You may notice under the table there is a mitre saw too.  I bought this so that I could cut the 50cm length bars to the correct lengths to match my stencils.  I would also have rails and legs to cut, so it seemed like a necessary thing to get.  I also bought a drill to drill holes for cords, and a router with which to tune the keys.  I mounted this under my workbench (a con...
Read more

First notes completed

So, when I wish to tune a new bar I mark on one side of the bar the centre line, and the points that correspond to the distances that are 25%, 30%, 35% and 40% from the end of the bar. I open Audacity and do a test recording of the bar before removing any material.  This is usually way above the frequency I am looking to reach, but it is nice to have a record of where I started. Then using a round tipped 20mm router bit which gives a nice smooth curve to my first cut, and using the 30% line as my guide, I move the bar over the router (which is mounted upwards from under the workbench).  I say that I use the 30% line as a guide, but in actual fact the edge of the router curve just touches the 25% line on the higher tone bars. Once I have my limits defined, I remove the remaining 6mm from between these two cuts. Next I raise the router to about 11mm.  I now make two more cuts using with the same router bit, making sure that the edge of the router does not cross the ...
Read more