Tuesday, March 24, 2009

Project description

I do not recall exactly how I came to the idea of this project. Certainly it was not something that happened at a certain moment, but rather developed in the back of my mind for some time until a point when I started to give more serious thoughts to the idea. It was probably triggered by my project of Bb bass clarinet extension down to C. For that project I needed to consider different cheap materials to perform acoustical studies in order to define the tone hole placement of the three tone holes for Eb, D and Db and additionally to adjust the extension length to properly place the tone hole in the bell for the lowest tone C. Once the proper tone hole layout was derived, a second step was to build the extension in some hard grain wood like grenadilla, cocobolo or rosewood. An obvious testing material for the acoustical studies was PVC tube. A natural offspring of that idea was to use the same approach to study the acoustics of an instrument twice as long, that I had few chances of ever seeing first hand. So, here is the project description.

  • Derive the dimensions and tone hole placement of a BBb contrabass clarinet.
  • Investigate acoustical effects of bends, flared bells, bore discontinuities at bends and couplings in harmonics spectrum, effects of tone hole diameters in cut-off frequencies at different registers; end corrections; etc.
  • Sound spectra measurements and harmonics analysis
  • Acoustic impedance measurements
Material: PVC tubing 1-1/4" schedule 40
Range: down to written C (sounding Bb0; 29,14 Hz)
Layout: Paperclip

Here is a first sketch of my original idea.

tone hole placement, the systematic approach as Theobald Boehm used for the flute in 19th century applies: to drill as many holes and as large as needed to achieve each and every note of the desired range, without wondering a priori about a keywork that would operate the resulting instrument or fingerings required.

Many would be at this point disappointed:
is it going to be a real instrument on the table ever?

The answer is that I do not know yet. The project as currently planned is challenging enough and may span easily through couple of years. It is not only to produce a perforated PVC tube. The project includes acoustics measurements for which I will have to develop measurement equipment and techniques using affordable components, since I do not have access to specialized devices such as an impedance spectrometer, for example. Moreover, once a reasonably perforated tube is obtained, there is no guarantee that the resulting acoustical qualities justify the sizable effort of developing the corresponding keywork.

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