Java sound generation generates noise

I'm using javax Sound to make sound, but when you play, they will make some noise in the background. If you play several notes at a time, it will even overcome the sound This is the code:

public final static double notes[] = new double[] {130.81,138.59,146.83,155.56,164.81,174.61,185,196,207.65,220,233.08,246.94,261.63,277.18,293.66,311.13,329.63,349.23,369.99,392,415.3,440,466.16,493.88,523.25,554.37};



public static void playSound(int note,int type) throws LineUnavailableException {          //type 0 = sin,type 1 = square

    Thread t = new Thread() {
        public void run() {
            try {

                int sound = (int) (notes[note] * 100);


                byte[] buf = new byte[1];
                AudioFormat af = new AudioFormat((float) sound,8,1,true,false);
                SourceDataLine sdl;

                sdl = AudioSystem.getSourceDataLine(af);

                sdl = AudioSystem.getSourceDataLine(af);
                sdl.open(af);
                sdl.start();
                int maxi = (int) (1000 * (float) sound / 1000);
                for (int i = 0; i < maxi; i++) {
                    double angle = i / ((float) 44100 / 440) * 2.0
                            * Math.PI;
                    double val = 0;
                    if (type == 0) val = Math.sin(angle)*100;
                    if (type == 1) val = square(angle)*50;

                    buf[0] = (byte) (val * (maxi - i) / maxi);
                    sdl.write(buf,1);
                }
                sdl.drain();
                sdl.stop();
                sdl.close();
            } catch (LineUnavailableException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        };
    };

    t.start();
}

public static double square (double angle){
    angle = angle % (Math.PI*2);
    if (angle > Math.PI) return 1;
    else return 0;
}

This code comes from: https://stackoverflow.com/a/1932537/3787777

Solution

In this answer, I will refer to 1) your code, 2) a better way (with all due respect:) and 3) playing two notes at the same time

Your code

First, the sampling rate should not depend on the note frequency So try:

AudioFormat(44100,...

Next, use 16 bit sampling (sounds better!) Here's your code to play a simple tone without noise - but I'll use it a little (see later) Please review the comments:

Thread t = new Thread() {
    public void run() {
        try {

            int sound = (440 * 100);        // play A
            AudioFormat af = new AudioFormat(44100,16,false);
            SourceDataLine sdl;
            sdl = AudioSystem.getSourceDataLine(af);
            sdl.open(af,4096 * 2);
            sdl.start();

            int maxi = (int) (1000 * (float) sound / 1000); // should not depend on notes frequency!
            byte[] buf = new byte[maxi * 2];   // try to find better len!
            int i = 0;
            while (i < maxi * 2) {
                // formula is changed to be simple sine!!
                double val = Math.sin(Math.PI * i * 440 / 44100);
                short s = (short) (Short.MAX_VALUE * val);
                buf[i++] = (byte) s;
                buf[i++] = (byte) (s >> 8);   // little endian
            }
            sdl.write(buf,maxi);
            sdl.drain();
            sdl.stop();
            sdl.close();
        } catch (LineUnavailableException e) {
            e.printStackTrace();
        }
    }
};

t.start();

Suggest better code

The following is a simplified version of the code, which can play some noiseless notes (frequencies) I prefer it because we first create a doubles array, which is a general value These values can be combined, stored or further modified We then convert them to (8 - bit or 16 - bit) sample values

private static byte[] buffer = new byte[4096 * 2 / 3];
private static int bufferSize = 0;

// plays a sample in range (-1,+1).
public static void play(SourceDataLine line,double in) {
    if (in < -1.0) in = -1.0;  // just sanity checks
    if (in > +1.0) in = +1.0;

    // convert to bytes - need 2 bytes for 16 bit sample
    short s = (short) (Short.MAX_VALUE * in);
    buffer[bufferSize++] = (byte) s;
    buffer[bufferSize++] = (byte) (s >> 8);   // little Endian

    // send to line when buffer is full
    if (bufferSize >= buffer.length) {
        line.write(buffer,buffer.length);
        bufferSize = 0;
    }
    // todo: be sure that whole buffer is sent to line!
}

// prepares array of doubles,not related with the sampling value!
private static double[] tone(double hz,double duration) {
    double amplitude = 1.0;
    int N = (int) (44100 * duration);
    double[] a = new double[N + 1];
    for (int i = 0; i <= N; i++) {
        a[i] = amplitude * Math.sin(2 * Math.PI * i * hz / 44100);
    }
    return a;
}

// finally:
public static void main(String[] args) throws LineUnavailableException {
    AudioFormat af = new AudioFormat(44100,false);
    SourceDataLine sdl = AudioSystem.getSourceDataLine(af);

    sdl.open(af,4096 * 2);
    sdl.start();

    double[] tones = tone(440,2.0);    // play A for 2 seconds
    for (double t : tones) {
        play(sdl,t);
    }

    sdl.drain();
    sdl.stop();
    sdl.close();
}

That sounds good

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