Implementation of a physics-based drum synthesizer in embedded environment

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Supervisor:
Dr. Bank Balázs Lajos
Department of Measurement and Information Systems

The sound of electronic music instruments plays more and more dominant role in the modern music. Many musical genres are based on special electronic sound. In my diploma thesis, I have designed and realized a drum synthesizer in embedded environment, which is able to generate electrical drum sounds.

The drum synthesizers available today are mostly based on pre-recorded sound sample playback. This playback is triggered by events generated by the sensor mounted on the electrical drum surface. It has a large disadvantage that the details of the playing disappear from the generated signal.

In my diploma thesis I have implemented a drum synthesizer which keeps the details of the playing in the generated output. My selected musical instrument was a cajon which has an Afro-Peruvian origin. Thus my solution is not only an electrical drum surface, it is an acoustic instrument. The synthesizer extends the acoustic instrument sound with electronic drum sounds.

I have analyzed sensors based on different technologies to decide which is the best for exciting the physics-based models. I have analyzed different piezo sensors, a force sensitive resistor, electromechanical microphone and an acceleration meter.

First of all, I have implemented the base units of the synthesis in Matlab. I have designed two models: one for lower sounds (like a big drum) and another one for higher sounds (like a snare drum) based on the typical cajon sounds. The basis of the physics-based drum models is the modal solution of the partial differential equation that describes the vibration of a circular membrane.

I have tested the models with signals of sensors which are mounted on my self-made cajon. Based on these tests, I have designed a preprocessing step to make a signal routing between the models according to the behavior of input signal in the frequency domain.

Based on the results of the testing in the modeling environment, I have implemented the drum sound synthesis to the floating-point Analog Devices SHARC ADSP-21489 digital signal processor and I made a touch screen based solution for the real-time parameter settings.

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