Beeper - loopable sound using Clip.

Question

// <applet code='Beeper' width='300' height='300'></applet>
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import java.text.DecimalFormat;
import javax.sound.sampled.*;
import java.io.ByteArrayInputStream;
/** Beeper presents a small, loopable tone that can be heard
by clicking on the Code Key.  It uses a Clip to loop the sound,
as well as for access to the Clip's gain control.
@author Andrew Thompson
@version 2009-12-19
@license LGPL */
public class Beeper extends JApplet {
public void init() {
  getContentPane().add(new BeeperPanel());
  validate();
public static void main(String[] args) {
  SwingUtilities.invokeLater(new Runnable() {
   public void run() {
    JFrame f = new JFrame("Beeper");
    f.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
    BeeperPanel BeeperPanel = new BeeperPanel();
    f.setContentPane(BeeperPanel);
    f.pack();
    f.setMinimumSize( new Dimension(300,300) );
    f.setLocationRelativeTo(null);
    f.setVisible(true);
/** The main UI of Beeper. */
class BeeperPanel extends JPanel {
JComboBox sampleRate;
JSlider framesPerWavelength;
JLabel frequency;
JCheckBox harmonic;
Clip clip;
DecimalFormat decimalFormat = new DecimalFormat("###00.00");
BeeperPanel() {
  super(new BorderLayout());
  JPanel options = new JPanel();
  BoxLayout bl = new BoxLayout(options,BoxLayout.Y_AXIS);
  options.setLayout(bl);
  Integer[] rates = {
   new Integer(8000),
   new Integer(11025),
   new Integer(16000),
   new Integer(22050)
  sampleRate = new JComboBox(rates);
  sampleRate.setToolTipText("Samples per second");
  sampleRate.setSelectedIndex(1);
  JPanel pSampleRate = new JPanel(new BorderLayout());
  pSampleRate.setBorder(new TitledBorder("Sample Rate"));
  pSampleRate.add( sampleRate );
  sampleRate.addActionListener(new ActionListener() {
   public void actionPerformed(ActionEvent ae) {
    setUpSound();
  options.add( pSampleRate );
  framesPerWavelength = new JSlider(JSlider.HORIZONTAL,10,200,25);
  framesPerWavelength.setPaintTicks(true);
  framesPerWavelength.setMajorTickSpacing(10);
  framesPerWavelength.setMinorTickSpacing(5);
  framesPerWavelength.setToolTipText("Frames per Wavelength");
  framesPerWavelength.addChangeListener( new ChangeListener(){
   public void stateChanged(ChangeEvent ce) {
    setUpSound();
  JPanel pFPW = new JPanel( new BorderLayout() );
  pFPW.setBorder(new TitledBorder("Frames per Wavelength"));
  pFPW.add( framesPerWavelength );
  options.add( pFPW );
  JPanel bottomOption = new JPanel( new BorderLayout(4,4) );
  harmonic = new JCheckBox("Add Harmonic", false);
  harmonic.setToolTipText(
   "Add harmonic to second channel, one octave up");
  harmonic.addActionListener( new ActionListener(){
   public void actionPerformed(ActionEvent ae) {
    setUpSound();
  bottomOption.add( harmonic, BorderLayout.WEST );
  frequency = new JLabel();
  bottomOption.add( frequency, BorderLayout.CENTER );
  options.add(bottomOption);
  add( options, BorderLayout.NORTH );
  JPanel play = new JPanel(new BorderLayout(3,3));
  play.setBorder( new EmptyBorder(4,4,4,4) );
  JButton bPlay  = new JButton("Code Key");
  bPlay.setToolTipText("Click to make tone!");
  Dimension preferredSize = bPlay.getPreferredSize();
  bPlay.setPreferredSize( new Dimension(
   (int)preferredSize.getWidth(),
   (int)preferredSize.getHeight()*3) );
  // TODO comment out to try KeyListener!
  bPlay.setFocusable(false);
  bPlay.addMouseListener( new MouseAdapter() {
    @Override
    public void mousePressed(MouseEvent me) {
     loopSound(true);
    @Override
    public void mouseReleased(MouseEvent me) {
     loopSound(false);
  play.add( bPlay );
  try {
   clip = AudioSystem.getClip();
   final FloatControl control = (FloatControl)
    clip.getControl( FloatControl.Type.MASTER_GAIN );
   final JSlider volume = new JSlider(
    JSlider.VERTICAL,
    (int)control.getMinimum(),
    (int)control.getMaximum(),
    (int)control.getValue()
   volume.setToolTipText("Volume of beep");
   volume.addChangeListener( new ChangeListener(){
    public void stateChanged(ChangeEvent ce) {
     control.setValue( volume.getValue() );
   play.add( volume, BorderLayout.EAST );
  } catch(Exception e) {
   e.printStackTrace();
  add(play, BorderLayout.CENTER);
  setUpSound();
/** Sets label to current frequency settings. */
public void setFrequencyLabel() {
  float freq = getFrequency();
  if (harmonic.isSelected()) {
   frequency.setText(
    decimalFormat.format(freq) +
    "(/" +
    decimalFormat.format(freq*2f) +
    ") Hz" );
  } else {
   frequency.setText( decimalFormat.format(freq) + " Hz" );
/** Generate the tone and inform the user of settings. */
public void setUpSound() {
  try {
   generateTone();
   setFrequencyLabel();
  } catch(Exception e) {
   e.printStackTrace();
/** Provides the frequency at current settings for
sample rate & frames per wavelength. */
public float getFrequency() {
  Integer sR = (Integer)sampleRate.getSelectedItem();
  int intST = sR.intValue();
  int intFPW = framesPerWavelength.getValue();
  return (float)intST/(float)intFPW;
/** Loops the current Clip until a commence false is passed. */
public void loopSound(boolean commence) {
  if ( commence ) {
   clip.setFramePosition(0);
   clip.loop( Clip.LOOP_CONTINUOUSLY );
  } else {
   clip.stop();
/** Generates a tone, and assigns it to the Clip. */
public void generateTone()
  throws LineUnavailableException {
  if ( clip!=null ) {
   clip.stop();
   clip.close();
  } else {
   clip = AudioSystem.getClip();
  boolean addHarmonic = harmonic.isSelected();
  int intSR = ((Integer)sampleRate.getSelectedItem()).intValue();
  int intFPW = framesPerWavelength.getValue();
  float sampleRate = (float)intSR;
  // oddly, the sound does not loop well for less than
  // around 5 or so, wavelengths
  int wavelengths = 20;
  byte[] buf = new byte[2*intFPW*wavelengths];
  AudioFormat af = new AudioFormat(
   sampleRate,
   8,  // sample size in bits
   2,  // channels
   true,  // signed
   false  // bigendian
  int maxVol = 127;
  for(int i=0; i<intFPW*wavelengths; i++){
   double angle = ((float)(i*2)/((float)intFPW))*(Math.PI);
   buf[i*2]=getByteValue(angle);
   if(addHarmonic) {
    buf[(i*2)+1]=getByteValue(2*angle);
   } else {
    buf[(i*2)+1] = buf[i*2];
  try {
   byte[] b = buf;
   AudioInputStream ais = new AudioInputStream(
    new ByteArrayInputStream(b),
    af,
    buf.length/2 );
   clip.open( ais );
  } catch(Exception e) {
   e.printStackTrace();
/** Provides the byte value for this point in the sinusoidal wave. */
private static byte getByteValue(double angle) {
  int maxVol = 127;
  return (new Integer(
   (int)Math.round(
   Math.sin(angle)*maxVol))).
   byteValue();
}

Answer 1

This code was written (rather belatedly) in response to a question in [Example: Code to generate audio tone|http://forums.sun.com/thread.jspa?threadID=5243872]. Due to it's age, it has been locked.
The replier wanted to know how to use JavaSound for a Morse code key. Actually now I think about it, the sound loops nicely, but it still demonstrates a slight click at start and stop. I tried using Clip.loop(0) to stop the sound, but that did not avoid the 'click'! I suppose you would need to do as the person was musing, and adjust the GAIN of the Clip up and down.
In any case - questions.
- Can anyone make this work for key presses? The first thing you'd need to do is a find on "TODO" and comment out the line that ensures the Code Key is not focusable (and then add a KeyListener(1)). The problem I encountered was that the KeyEvents were getting fired continuously, which caused the sound to 'stutter'. A Timer to ignore quickly repeated keys might work (though I could not make it work for me), but then that would introduce a lag between when whe key was released, and when the sound stopped. It would need to be a very short delay, to use it much in the way the mouse click currently works.
- Any ideas on improvements to the basic code? (1) (I will be adding the ability to configure the parameters of the applet - more code lines. Possibly also converting the GAIN control from the mostly useless logarithmic ..whatever scale it uses, to linear.)
1) Note that I had to use single spaces to indent - everything else blew the posting limit(2).
2) Hence also, questions on 2nd post. ;)
To compile and run as an applet/application (in a recent SDK).
javac Beeper.java
appletviewer Beeper.java
java BeeperEdit 1:
Latest source can be found at [http://pscode.org/test/eg/Beeper.java]. See also the [formatted version|http://pscode.org/fmt/sbx.html?url=%2Ftest%2Feg%2FBeeper.java&col=2&fnt=2&tab=2&ln=0].
Edited by: AndrewThompson64 on Dec 19, 2009 1:50 PM