import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;

/**
 * Commands to generate and play sound file:
 *
 *  $ avconv -f f64le -ar 44100 -ac 1 -i /tmp/snd.raw /tmp/snd.wav
 *  $ mplayer /tmp/snd.wav
 *
 */
public class SndGen {
    public static void main(String[] args) throws IOException {
        double freqs[]=new double[]{440, 660, 880};
        double amplitudes[]=new double[]{.5,.3,.2};
        double sampleFreq=44100;
        double lengthInSecs=5;
        int nSample=(int)(lengthInSecs*sampleFreq);
        ByteBuffer bb=ByteBuffer.allocate(8);
        bb.order(ByteOrder.LITTLE_ENDIAN);
        byte[] buffer=new byte[8];
        try(FileOutputStream fos=new FileOutputStream("/tmp/snd.raw"))
        {
            for(int i=0;i<nSample;++i)
            {
                double t=i*1.0/sampleFreq;
                double sample=0;
                for(int j=0;j<freqs.length;++j)
                {
                    double omega=freqs[j]*2.0*Math.PI;
                    sample+=amplitudes[j]*Math.sin(omega*t);
                }
                bb.clear();
                bb.putDouble(sample);
                bb.flip();
                bb.get(buffer);
                fos.write(buffer);
            }
        }
    }
}