Lags while playing 2 sounds on the same time in timer

I have a small app that basically sets up a timer and plays sets of 2 sounds one after another.

I've tried 2 timers, because I wanted both sounds to start exactly at the same time each time. I gave the app 500ms for setting both timers before they start

    Calendar cal = Calendar.getInstance();
    Date start = new Date(cal.getTime().getTime() + 500);

    timerTask1 = new TimerTask() { //1st timer
      @Override
      public void run() {
          soundManager.playSound(1);
      }
    };
    timer1 = new Timer();
    timer1.schedule(timerTask1, start, 550);


    timerTask2 = new TimerTask() { //2nd timer
      @Override
      public void run() {
          soundManager.playSound(2);
      }
    };
    timer2 = new Timer();
    timer2.schedule(timerTask2, start, 550);
}

soundManager is a SoundManager object which is based on this tutorial. Thew only change I've made was decreasing number of avalible streams from 20 to 2 since I play only 2 sounds at the same time.

Now the problem. It's not playing at the equal rate neither on my Motorola RAZR or the emulator. The app slows sometimes, making a longer brake than desired. I can't let that happen. What could be wrong here?

I'm using very short sounds in OGG format

EDIT: I've made some research. Used 2 aproaches. I was measuring milisecond distances between sound was fired. Refresh rate was 500 ms.

• 1st aproach was TimerTask - it is a big fail. It started at 300ms, then was constantly growing, and after some time (2 mins) stabilized at 497ms which would be just fine if it started as that.
• 2nd aproach was while loop on AsyncTask - it was giving me outputs from 475 to 500ms which is better than TimerTask but still inaccurate

At the end none of aproach was playing smoothly. There were always lags