The aim of this work was to investigate theoretically and experimentally the fact that it is possible to create sound by using the nonlinearity in air. A speaker was built verifying the theory that if at least two high frequencies at high amplitude is propagating through a nonlinear medium, for example air, the difference frequency of these two is created in mid air. Measurements and simulations were performed on what the pressure distribution from a ultrasonic transducer looks like.
Contents
1 NOTATION
2 INTRODUCTION
3 VIBRATIONS AND SOUND
4 BASICS OF NONLINEAR ACOUSTICS
4.1 DIFFERENCE AND SUM FREQUENCY
5 RADIATION FROM A BAFFLED PISTON
5.1 DERIVATION OF RAYLEIGH INTEGRAL
5.2 TIME HARMONIC SIGNALS
5.3 CIRCULAR ELEMENTS
5.4 RECTANGULAR ELEMENTS
5.5 ARRAY OF ELEMENTS
6 THE SPEAKER
6.1 BUILDING THE SPEAKER
6.2 CREATING THE SIGNAL
6.3 MEASURING THE SPEAKER
7 DISCUSSION AND CONCLUSION
8 REFERENCES
9 APPENDIX MATLAB SCRIPTS
9.1 STATUSBAR.M
9.2 UPDATESTATUSBAR.M
9.3 PRESSUREAXIS_2O5.M
9.4 PRESSUREOFAXIS_2O5.M
9.5 PRESSURE_RECT_4O10.M
Author: Johan Fredin
Source: Blekinge Institute of Technology
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