1. Virtual Guitar
Pasi Marttila
COMSOL Oy
+358 9 2510 4051

2. Outline
Introduction
Tuning Fork: Validate and Verify
Virtual Guitar: Design and Innovate
Conclusion
Q & A
3. Introduction
What do we understand with Virtual Guitar?
Synthesizer vs. Physical simulation model
Modeling and simulation
Some key terms: model, simulation model and analysis
What information these models can tell us?
What else we can do with such virtual models?
4. Lets Tune Our Instruments First!
http://www.ultimate-guitar-tuner.com/standard-tuning/
5. Tuning Fork: Validate and Verify
Classical example: Tuning Fork
Eigenmode analysis to verify the design: Here we compute the fundamental eigenfrequency and eigenmode of a tuning fork. When correctly designed, the tuning fork vibrates at 440 Hz, a frequency known as standard concert pitch.
Forced responce analysis to hear the tone and fine tune the model: Here we excite the structure with a known frequency and study the response of the structure both visually and tonally.
Acoustic-structure interaction: Final step is to study the acoustic pressure field generated by the vibrations of the prongs.
6. Tuning Fork: Validate and Verify
Tuning Fork: Eigenmode analysis
Analysis is used to verify the dimensions of the fork (length of the prongs) to meet the design parameters
... to verify the material properties for this specific design (mechanical)
... to verify the numerical accuracy
... to validate the chosen simulation method so that we can rely on the results
7. Tuning Fork: Validate and Verify
In frequency response analysis the structure will be excited with harmonical load at given frequency
Air domain over the fork has also been simulated while acoustical pressure field created by vibrating prongs can be identified
8. Tuning Fork: Validate and Verify
And it sounds like this ...
9. Virtual Guitar
http://www.publicdomainpictures.net/
10. Virtual Guitar: Design and Innovate
Three different analysis has been made
Eigenfrequency analysis to find the eigenmodes and shapes of the guitar
Forced responce analysis with acoustic coupling to study the structural and acoustic response of the guitar in a harmonically loaded case
Time-dependent analysis to produce the sound of the guitar while all the dynamics and damping effects has been taken into account
Simulation assumptions:
We imitate the vibrating string by applying the surface load to the bridge
Vibration has been modeled as a damped time-dependent load case
11. Virtual Guitar: Eigenfrequency Analysis
First guitar model: Eigenfrequency and mode analysis
Only structural effects are in the simulation
With such model we can find eigenfrequencies (resonance) of the structure
As an output we get both the actual frequencies and the shape how structure vibrates
12. Virtual Guitar: Eigenfrequency Analysis
13. Virtual Guitar: Frequency Response Analysis
Second guitar model: Forced response analysis in frequency domain
Both acoustical and structural effects are in the simulation
With such model we can simulate single frequencies and frequency sweeps while certain components are harmonically loaded (bridge in this case)
As an output we get both the structucal response of the guitar and the acoustic pressure field of the simulated air domain
14. Virtual Guitar: Frequency Response Analysis
15. Virtual Guitar: Frequency Response Analysis
16. Virtual Guitar: Transient analysis
Third guitar model: Time-dependent simulation with sampling frequency in audio range (22050Hz in this case)
Both acoustical and structural effects are in the simulation
Critical design parameters for simulation are material settings including the damping effects
With such model we can study how guitar structure behaves and what kind of sound it produces
Simulations are time hungry and requires lots of wall clock time to run
17. Virtual Guitar: Transient analysis
18. Virtual Guitar: Transient analysis
19. Virtual Guitar: Transient analysis
And it sounds like this ...
20. Conclusion
Modern simulation and modeling techniques are useful while designing musical instruments
Material knowledge acts key role when producing reliable simulation results
Eigenfrequency and frequency response analysis can be run in minutes while full transient simulations might take days
Machinery is already available, computing power is cheap and simulation knowledgeistaughtat universities = Virtual Guitar is reality today!
THANK YOU!
21. Q & A