class GuitarString {

    public void tic() {
        // TODO: Dequeue the front sample and enqueue a new sample that is
        //       the average of the two multiplied by the DECAY factor.
        //       Do not call StdAudio.play().
        double first = buffer.dequeue();
        buffer.enqueue((first + buffer.peek()) * DECAY / 2);
    }

    public  GuitarString(double frequency);

}