void Update()
    {
        if (durationToSoundLiftoff < 0.0f)
        {
            durationToSoundLiftoff = randomFloat(minDurationToSound, maxDurationToSound);
        }

        if (stopWatch.execeedesMilliseconds((int)durationToSoundLiftoff))
        {
            AudioSource liftoffSound = GetComponent <AudioSource>();
            liftoffSound.Play();

            durationToSoundLiftoff = -1.0f;
            stopWatch.reset();
        }
    }