Friday, April 10, 2009

First sound

The mouthpiece fixation socket has an outer diameter of 37mm. Therefore, it was necessary to machine in the lathe a piece of tubing to increase the inner diameter from 34mm to 37mm in order assemble the mouthpiece to the PVC tube. This was done in my trusty Unimat 3, of Austrian manufacture, as seen in the picture below.



With this machined piece of tube, a 45deg elbow, a 90deg elbow, about 1m of tubing and a coupling, I assembled an instrument to resemble the air column of a standard Bb bass clarinet. The overall length of piping without considering the mouthpiece was about 120cm. The coupling was used at the end for tuning to Db2 (69.3 Hz), which corresponds to written Eb in a Bb transposition instrument. I did not have a contrabass clarinet ligature to attach the reed to the mouthpiece. Since I did not want to spend in superfluous accesories a
nd wait for the ligature to be shipped, I came to the idea of using a piece of string in the same fashion as German system clarinetists have been using for their Oehler and Wurlitzer mouthpieces for centuries. It worked so well, that I will be keeping this feature as a standard. The red string can be seen in a picture below.

To get an impression of the beast assembled, here is a comparison with other instruments. There is a Bb bass clarinet Evette - Buffet Crampon down to Eb (Db2) and a french basson Buffet Crampon (Bb1 - 58.27 Hz).




Many will be wondering already about what kind of bassoon is this. It does not look at all like the bassoons you see bassoonists playing nowadays! Well this is actually true, only if you think of Thünemann, Turkovic, Andrea Merenzon and 98% of the rest of world bassoonists. However, there is still as small stronghold of French basson in some orchestras in France, for example the Orchestra of the National Opera in Paris (even if Laurent Lefevre switc
hed to German bassoon).

In general the bore of the French bassoon is narrower and it has a different tonal quality, being brighter and more nasal, as opposed to the darker tone of the German bassoon.

Why do I care, after all, about the French bassoon?

I may at this point argue that I specially like that nasal tone of the French bassoon, that the particular acoustic characteristics, the easiness with which the high register reacts, the formants' frequencies of such an instrument, etc, etc, etc. However, I believe it is just that chivalrous attitude in me. I am a gentleman, as you may have noticed, therefore I champion "lost" causes.

Here is an article from the Journal of the International Double Reed Society on the current situation of the French bassoon. Here is a more technical article about tone, reeds and fingerings in the French bassoon.

After the digression on French bassoon, now back to the main topic of the day: first sound of the PVC tube of 34 mm internal diameter using a standard BBb contrabass clarinet mouthpiece.
I did not find a way to import .wav files to the blog, thus I am posting a video instead and then taking the opportunity to show the electronic tuner to document that I am actually in tune. Unbelievable! The note being played is Db2 (69.3 Hz). I am attaching also a frequency spectrum analysis using the standard microphone I use with the PC for chatting and a software called CoolEdit. This software is able to calculate the Fast Fourier transformation of the input sound using different types of sampling windows. Through the Fourier transformation, basically the waveform is decomposed in a series of superimposed sinusoidal signals of different amplitudes that add up to the waveform in question. Therefore the analysis of the waveform in terms of the time domain can be transformed to the frequency domain and the different frequencies of which the waveform is composed can be resolved.

I know this is a very modest experimental setup for acoustical research, but in any case it may serve the purpose to illustrate a few ideas.

PVC tube - Db2: sound
video

PVC tube - Db2: Fast Fourier Transform
The fundamental frequency along with the 3rd and 5th can be seen clearly prevailing over the whole spectrum as was to be expected. The fundamental shows the higher intensity. However, there is also some intensity of the 2nd and 4th harmonics. Compare with the bass clarinet spectrum farther below, and it may be noticed that there the 2nd harmonic is practically not visible and the intensity of the 4th is very low. The main difference between this two air columns is that the PVC has a bore of 34mm and the bass clarinet a bore of 24mm. Another difference is that the bass clarinet lowest note speaks through the bell flare, whereas for the PVC tube the cylindrical bore ends abruptly. This effect bears, in any case, not relevance at the low frequency range being analysed (less than 1khz).

Bb bass clarinet - Db2: sound

video

Bb bass clarinet - Db2: Fast Fourier Transform


French bassoon - Db2: sound
video

French bassoon - Db2: Fast Fourier Transform

The characteristics tonal quality of the bassoon is heavily influenced by strong formants in a range of about 450 to 500Hz. Therefore, there is a peak of intensity of the harmonics neighbouring the formants frequency range (6th and 7th). A formant is a specially favoured frequency range that enters in resonance even with different fundamentals. It is an essencial concept in phonetics, speech analysis and linguistics.

This can be clearly seen in the plot below, where the 6th and 7th harmonics show a higher intensity than the rest. On the other hand, the fundamental frequency of 69.3 Hz shows a relatively low intensity. This low intensity of the fundamental frequency is probably the cause why the electronic tuner has a hard time deciding that I am actually 20 cents too flat (see video attached). The wavering pitch you hear was done on purpose, just to get the tuner to react. OK, I reckon I am not a trained bassonist after all and my sound emission leaves to be desired.

2 comments:

  1. Bertino, estas pirucho totalmente, que eso de Fourier. Me imagino que unas ecuaciones diferenciales que no tienen solucion cerrada y hay metodos de aproximacion... En fin, me encanto lo de que los gentlemen solo persiguen causas perdidas. Tiene un tufillo Oscar Wilde.

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