Let's face it, potato chips have to be one of the most noisy food invented. They come in this crinkly foil bag most times that just doesn't want to quit. It's bad enough trying to get it open, the more you try to do it quietly, the louder it protests and the longer drawn the task of opening that simple bag of chips gets. Surprisingly, most of the noise actually comes from the preparation bit and the ripping bit is actually rewardingly crisp and rather quiet. Of course if you elbow your neighbours in the process things may take an ugly turn.
Second method is recommended for ninjas, cutthroats or anyone with a sharp blade.
The rest is obvious. Each time you munch on that chip, envious ears within a four seat radius can clearly hear which one of your molars was responsible. High scoring on the satisfaction scale with the most ventilation, but awfully indiscreet. Secondly, mouth closed and munch. Pretty good for small chips, not recommended for big chips unless you've got a mouth-span like Jacintha.