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Examination of the Influence of Different Mouthpiece Forms on the Resonance Behavior of Trumpets


The mouthpiece of the trumpet is the interface between instrument and musician, and represents one of the brass instrument's most sensitive parts. Besides the influence of the embouchure, the form of the mouthpiece has a great effect on the intonation of the entire instrument. In order to observe the influence of varying mouthpiece forms on the input impedance-and consequently the intonation- of the trumpet, the resonant frequencies of a trumpet with varied mouthpieces were calculated with the help of a computer model (Simulation PMP).

Using the standard Viennese mouthpiece as a point of departure, the following factors were successively varied:

Standard mouthpiece bore  IWK Institut of Music Acoustics (Wiener klangstil)

Fig.1: Standard mouthpiece, x axis length [m], y axis radius [m]

During all variations, except for the cup variation with constant cup volume, the total length, the initial radius, and the terminal radius were held constant.

Variation of the cup form

Figure 2 shows the examined cup form. Figures 3 and 4 show the influence of mouthpiece and trumpet resonance resulting from the variation in the cup form.

different cup forms IWK Institut of Music Acoustics (Wiener klangstil)

Fig.2: The different cup forms

mouthpiece resonance variation of the cup form IWK Institut of Music Acoustics (Wiener klangstil)

Fig.3: Changes to the mouthpiece resonance relative to the standard mouthpiece through variation of the cup form

trumpet resonance variation of the cup form IWK Institut of Music Acoustics (Wiener klangstil)

Fig.4: Changes to the trumpet resonance relative to the trumpet with a standard mouthpiece through variation of the cup form

Enlargement of the cup volume results in a decrease in the trumpet resonance, while decreasing the cup volume raises it. Resulting shifts vary as much as 30 cent (the extreme variable of the cylindrical cup was as much as 180 cent). Nevertheless, this effect is not the sole influence of cup volume! In order to clarify this point, a further series of cup form variables with constant volume was studied. The mouthpiece forms are shown in Figure 5.

Mouthpiece with different cup form but constant volume IWK Institut of Music Acoustics (Wiener klangstil)

Fig.5: Mouthpiece with different cup form but constant volume

As seen in Figure 5, one cylindrical cup form and various conical cup forms were examined. Despite their purely theoretical basis, these forms illustrate clearly that trumpet resonance is not only influenced by the cup volume, but also the cup form. It should be noted that the length of the mouthpieces were varied. This shortening of the cylindrical portion was compensated so that the overall length of the instrument would be held constant.

trumpet resonance  variation of the cup form IWK Institut of Music Acoustics (Wiener klangstil)

Fig.6: Changes in the trumpet resonance relative to the trumpet with cylindrical cup during variation of the cup form

Variation of the bore

Figures 7& 8 show the influence of bore variation on the resonance of the mouthpiece and trumpet.

Displacement of mouthpiece resonances by varying the bore  IWK Institut of Music Acoustics (Wiener klangstil)

Fig.7: Displacement of mouthpiece resonances by varying the bore

Displacement of trumpet resonances by varying the bore IWK Institut of Music Acoustics (Wiener klangstil)

Fig.8: Displacement of trumpet resonances by varying the bore

Changing the bore diameter from 3mm to 5.4mm displaced resonances far less than altering the cup form. The mouthpiece resonance varied up to 80 cent, the trumpet resonance up to 10 cent. It is remarkable that in the example shown, expansion of the bore decreased the first four trumpet resonances and raised the rest (and vice versa).

Variation of the backbore

The following illustrations show mouthpieces with different backbores.

mouthpiece backbore  IWK Institut of Music Acoustics (Wiener klangstil)

Fig.9: Standard mouthpiece, x axis length [m], y axis radius [m]

mouthpiece backbore  IWK Institut of Music Acoustics (Wiener klangstil)

Fig.10: mouthpiece with conical backbore , x axis length [m], y axis radius [m]

mouthpiece backbore  IWK Institut of Music Acoustics (Wiener klangstil)

Fig.11: Mouthpiece with somewhat bulgy backbore, x axis length [m], y axis radius [m]

Figures 12 & 13 show the displacement of mouthpiece and trumpet resonance relative to the resonance frequency of the standard mouthpiece.

mouthpiece backbore  IWK Institut of Music Acoustics (Wiener klangstil)

Fig.12: Displacement of mouthpiece resonances by varying the backbore

mouthpiece backbore  IWK Institut of Music Acoustics (Wiener klangstil)

Fig.13: Displacement of trumpet resonances by varying the backbore

Summary

Based on this data, it is possible to make specific improvements intonation of the mouthpiece.

Since a specific type of mouthpiece is used in Vienna, there is not only a unified sound characteristic among trumpets, but there is also a more or less homogeneous trend in intonation.

 

 

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