Playing default android sound of button, clicking onTouch() method

In my android app I have some buttons, that should work with onTouch() method, course I need to change button's text, when finger in ACTION_DOWN position. But this buttons should to play default android sound of button clicking (like in onClick() method). Where I can find such sound? I think, it must be in SDK, but how can I find it? And what methods are better for such operation? I'm using MediaPlayer.

Listing:

public boolean onTouch(View v, MotionEvent event) {
    int action = event.getAction();
    switch (action) {
    case MotionEvent.ACTION_DOWN:
        addTextShadow(v);
        Log.v(LOG_TAG, "ACTION_DOWN");
        break;
    case MotionEvent.ACTION_MOVE:
        clearTextShadow(v);
        isMoved = true;
        Log.v(LOG_TAG, "ACTION_MOVE");
        break;
    case MotionEvent.ACTION_UP:
        Log.v(LOG_TAG, "ACTION_UP");
        if (!isMoved) {
            clearTextShadow(v);
            if (v.getId() == R.id.btn_new) {
                Log.v(LOG_TAG, "New pressed");

                            playSound(); //MY METHOD TO PLAY SOUND

            } else if (v.getId() == R.id.btn_saved) {
                Log.v(LOG_TAG, "Saved pressed");
            } else if (v.getId() == R.id.btn_random) {
                Log.v(LOG_TAG, "Random pressed");
            }
        }
        isMoved = false;
        break;
    }
    return true;
}

And my playSound() method:

    public void playSound(){
    if (mp != null) {
        mp.release();
        mp = null;
    }
    try {
        mp = MediaPlayer
    .create(MyActivity.this, R.raw.sound); //BUT HERE I NEED DEFAULT SOUND!
        mp.start();
    } catch (Exception e) {
        e.printStackTrace();
    }
}