With BIOS it´s just like a miracle
...Brass Instrument Optimization Software
With BIOS it´s just like a miracle
...
The Brass Instrument Optimization Software BIOS
Specifying optimization parameters and targets
Monitoring the optimization run on the fly
Optimization of a Natural Trumpet in D-Flat
Optimization of a Trumpet in D-Flat
Optimization of a Trumpet in B-flat with 3 Valves
more information on this subject
Numerical Model for Calculation of the Input Impedance of Brass Instruments |
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Optimization Algorithm |
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| Computer Program for Brass Instrument Optimization |
In the past the design of a new brass instrument was a trial and error procedure. Although experience of makers was growing and growing most instruments are still suffering from intonation errors.
Today it is possible to compute the acustical behavior of brass instruments by physical modeling techniques.
This way an instrument maker can evaluate "virtual" modifications and their influence on the acustical characteristics of an instrument without having to build it physically.
In a next step the computer can take over the search for geometry modifications changing the acoustical characteristics in the desired direction meeting performance targets as close as possible.
The Brass Instrument Optimization Software BIOS
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| Entering the instrument´s initial geometry |
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| Selecting coordinates to be released for optimization |
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| Defining optimization targets (Intonation, impedance envelope) |
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| Running the program |
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| Obtaining a proposal for a new geometry |
Specifying optimization parameters and targets
Monitoring the optimization run on the fly
Entering the instrument's initial geometry:
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Keep computing time short " reduce number of breakpoints |
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Opening angle small (tube) " bigger distances between outline points |
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Opening angle large (bell) " grid has to be much narrower |
Use optimizer to improve initial geometry:
If geometry cannot be measured with sufficient accuracy match simulated and measured impedance first using the optimizer. Release uncertain coordinates using a variation range corresponding to your estimated measurement error.
Carefully consider modification areas:
Check whether modifications in a place later on can actually be applied to the instrument!
Find a good starting position:
Essential to get a desired result fast. Experience and expertise of instrument makers can help to find a good starting position. Knowledge about sound pressure amplitudes of standing waves can help to determine the right place for a modification.
Measure the instrument to get actual performance:
In the target function desired improvements compared with the actual performance should be specified. The actual status can be obtained by a measurement or by a subjective judgement made by an expert player.
Establish priorities to guide a compromise
Define weights for your optimization targets.
Optimization of a Trumpet in B-Flat
An experiment has been made using a custom made trumpet in B-flat. This instrument is straight without any bend and has no valve. The goal was the improvement of the measured intonation of the instrument.
For practical reasons modifications have been restricted to the insertion of a metal sleeve (length 4 cm, wall thickness 0,5 mm) in the cylindrical part of the trumpet. The simple task was to find the optimum position of the sleeve.
Diagram 1 shows that even this little intervention caused a significant improvement of intonation.
Diagram 1: Measured intonation error before (red) and after (black) optimization
Optimization of a Natural Trumpet in D-Flat
A more difficult application of the optimizer was the improvement of the intonation of a natural trumpet in D-flat. The goal was to shift the 11th and the 13th resonance peak. Each of those peaks is positioned between two notes, both of which can be played modulating the pitch using the lips.
The first attempt was a pure intonation optimization. After a while the optimizer showed perfect intonation meaning that all intonation targets have been met. Looking at the input impedance of the modified instrument which is shown in figure 1 it can be recognized that the proposal is not very useful.
Fig. 1: Calculated impedance after first optimization
Fig. 2: Measured impedance after second optimization
In a second attempt the shape of the impedance curve was included in the optimization. After some attempts a reasonable compromise could be found which was partially implemented by the manufacturer. Although not all proposed modifications have been made - only those which were considered to be significant - a visible improvement of the crucial tones (Tab. 1) was achieved.
11.Peak |
13.Peak | |
| Target intonation | + 60 Cent |
+ 80 Cent |
| Initial intonation | + 67 Cent | + 57 Cent |
| Measured intonation | + 69 Cent | + 70 Cent |
| after modification |
Tab.1: Comparsion of target, initial and final intonation
Optimization of a Trumpet in B-flat with 3 Valves
In this example all valve combinations of a
standard trumpet have been optimized in parallel. The goal was a perfect intonation of all
playable notes.
No restrictions have been given to the
impedance envelope and the complete geometry was released for modification.
Initial intonation is shown in Diagram 1 while
intonation and impedance results are presented in Diagrams 2 and 3.
Diagram 1: Calculated intonation error before optimization
Diagram 2: Calculated intonation error after optimization
Diagram 2: Calculated impedace after optimization all valves pressed
More information on this subject:
Optimization of Brass Wind Instruments (1999)
Part I: Concept and Implementation (1999)
Part II: Applications, Practical Examples (1999)
last update: 09.07.2004
