CombustionEngine demo

Author: Kees van den Doel

A model of a four-stroke combustion engine. The driving force is obtained by constructing a looping audio sample, divided into four regions which represent the 4 stages of the engine: An intake stroke, a compression stroke (silence), a combustion stroke, and an exhaust stroke. The intake stroke was modeled as white noise enveloped with a bell curve. The exhaust stroke is modeled as white noise, rapidly decaying in time, inspired by a high pressure gas mixture being released when the valve opens. The combustion stroke consists of an enveloped burst of 1/f noise.

The sample is looped at adjustable rate, corresponding to the running speed of the engine. For added realism the engine is allowed to "misfire" once in a while, which is implemented by skipping a section in the looped sample.

The engine resonance frequencies and dampings can be scaled with the bottom two sliders. When the sound gets too soft press Stop/Start to reset AGC.

Source code:

import jass.render.*;
import jass.engine.*;
import jass.generators.*;
import java.net.*;

/**
   Combusion engine model
   @author Kees van den Doel (kvdoel@cs.ubc.ca)
*/
public class EngineApplet extends AppletController {

    ErraticLoopBuffer cylinders;
    SourcePlayer player;
    ModalObjectWithOneContact engineResonances;
    boolean isOn = true;
    float factor=1;
    String syfile = "../data/stick.sy";
    String wavfile = "../data/car2.wav";
    
    public void setNSliders() {
        nsliders = 4;
    }

    public void setNButtons() {
        nbuttons = 1;
    }

    public void init() {
        super.init();
        syfile = getParameter("syfile");
        wavfile = getParameter("wavfile");
    }
   
    public void start() {
        float srate = 44100.f;
        int bufferSize = 128*4;
        int bufferSizeJavaSound = 8*1024;
        URL codebase = getCodeBase();
        URL syurl = null;
        URL wavurl = null;
        try {
            syurl = new URL(codebase,syfile);
            wavurl = new URL(codebase,wavfile);
        } catch(MalformedURLException e) {
            System.out.println(e+" Malformed URL: " +codebase+" "+ syfile);
        }
        cylinders = new ErraticLoopBuffer(srate,bufferSize,wavurl);
        player = new SourcePlayer(bufferSize,bufferSizeJavaSound,srate);
        ModalModel mm = null;
        try {
            mm = new ModalModel(syurl);
        } catch(java.io.IOException e) {
            System.out.println(this+" "+e);
        }
        engineResonances = new ModalObjectWithOneContact(mm,srate,bufferSize);
        try {
            player.addSource(engineResonances);
            engineResonances.addSource(cylinders);
        } catch(SinkIsFullException e) {
        }
        float speed0 = 3;
        cylinders.setSpeed(speed0);
        float beatupness0 = 0.04f;
        String[] names = {"Speed ", "Beatupness ", "Damping ", "Size "};
        double[] val =   {speed0,   beatupness0,   1,          1      };
        double[] min =   {speed0,   0,             .5,         .4     };
        double[] max =   {15,       .1,            1,          2      };
        cylinders.setMisfireProb(beatupness0);
        setValues(val,min,max,names);
        jButton[0].setText ("Stop");
        
        player.start();
        isOn = true;
    }

    protected void jButtonMousePressed (int k,java.awt.event.MouseEvent evt) {
        switch(k) {
        case 0:
            if(isOn) {
                jButton[0].setText ("Start");
                isOn = false;
                cylinders.setVolume(0);
            } else {
                jButton[0].setText ("Stop");
                isOn = true;
                player.resetAGC();
                cylinders.setVolume(1);
            }
            break;
        }

    }
    
    protected void onSlider(int k) {
        switch(k) {
        case 0:
            cylinders.setSpeed((float)(super.val[0]));
            break;
        case 1:
            cylinders.setMisfireProb((float)super.val[1]);
            break;
        case 2:
            engineResonances.setDamping((float)super.val[2]);
            break;
        case 3:
            engineResonances.setFrequencyScale((float)super.val[3]);
            break;
        }
    }
}