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Clarinet Voicing for geeks

Author: Phat Cat
Date: 2003-09-03 12:27

Here are a pair links to articles on the physics of voicing in woodwind instruments and the clarinet:

http://www.phys.unsw.edu.au/~jw/reprints/FritzEtAl.pdf

http://www.phys.unsw.edu.au/~jw/reprints/tongueSMAC.pdf

These are pdf files of papers published by physicists in Proc. Stockholm Music Acoustics Conference. For those of you whose idea of a good time does not include curling up with a good set of mathematics equations, I’ll attempt a summary.

Even moderately advanced clarinetists know that voicing plays an important role in the production of a fine clarinet sound. Voicing involves the shape and position of the various members of the oral cavity, especially the glottis and the tongue. It is so named because such adjustments account for the differences between various vowel sounds, and it is often taught by such descriptions as the “eeee” or “ahhhh” position of the tongue. These adjustments affect the timbre (color, quality, brightness/darkness) of the tone as well as the pitch.

The authors of the above referenced articles use mechanical set-ups to measure various effects described by musicians. They also develop mathematical models to account for the observed measurements. Essentially, the vocal tract is impedance coupled acoustically to the bore of the clarinet through the opening between the reed and the mouthpiece. When the tongue is low, the impedance of the vocal cavity is very small compared to that of the clarinet bore and has negligible effect. When the tongue is high, it acts as an impedance matching transformer linking the small volume of the vocal tract to that of the clarinet bore. In laymen’s terms, with appropriate positioning of the tongue, the vocal tract becomes an extension of the resonating body of the interior of the clarinet.

This mechanism is similar to what happens when a professional singer voices his/her tone, but is not identical. In the case of the singer, the sound production mechanism is the vocal chords. The vocal/nasal cavity acts as THE resonating chamber, emphasizing some tones and deemphasizing others. For example, measurements have demonstrated that certain positioning of the throat elicits prominent harmonic resonances called formants that give opera voices their distinct sound. Finally, the audible components of the sound emerge from the mouth and to a lesser extend the nose.

In the case of the clarinet, the sound production mechanism is the reed and the primary resonance chamber is the interior of the clarinet, including the mouthpiece chamber, the barrel and a length of the clarinet bore depending on what note is fingered. The audible sound emerges from the body of the instrument: from the bell for the long-fingered notes and from tone holes for other notes. When the vocal cavity is properly formed—that is, the sound is voiced—the vocal cavity becomes an extension to the resonating chamber. This changes the timbre and pitch of the produced note, just as do changes in bore geometry (e.g., poly-cylindrical bore) and bore length (raising/lowering a key or pulling the barrel). However, the audible sound still emerges from the body of the clarinet.

Although this particular article does not address it specifically, no audible sound is contributed by the vocal chamber itself. The sound waves generated in the vocal cavity by the reed cannot emerge directly because the lips seal the mouthpiece and the nasal passage is closed off. Body tissue dampens any sound passing through it to a level far below audibility compared to the sound level emerging from the clarinet bore. The audible effect of voicing is by modifying the resonance properties of the clarinet bore not by adding separate sounds to it.

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