There is a way to make a timer that works when the Device is locked?

Question

I'm searching a way to make a chronometer that every 5 seconds emits a sound. The problem is that when the device is locked the timer obviously stops (because the CPU goes in sleep mode).

My code:

final Runnable r = new Runnable() {
    public void run() {
         chronsound.start();//Emit the sound
         customHandler.postDelayed(this,5000);
    }
};

There is a way to do this WITHOUT using the WakeLock? Thank you!