HowTo: play a sound effect once with new AudioSystem

I have been experimenting with particles and such now couple days. Yesterday evening I decided to add some booms to my app but I could not get sound out. Example in test worked ok but my attempt to play a sound effect once was dead silent.

The problem turned out to be that I had to set volume for the AudioTrack. I guess the volume in AudioPlayer is not set otherwise.

Here is a simple example, modified from TestJmexAudio.

protected void simpleUpdate() {
   if (timeToBoom && !sfx.isPlaying()) {
   // should I  also add sfx.stop() ???

protected void simpleInitGame() {
   audio = AudioSystem.getSystem();
   sfx = getSFX(Kaboom.class.getResource("firework_3.wav"), false);

private AudioTrack getSFX(URL resource, boolean loop) {
   AudioTrack sound = AudioSystem.getSystem().createAudioTrack(resource, false);
   return sound;