Put a microphone inside and outside the fridge. If the noise coming from inside the fridge is louder than the noise from outside the fridge, pop the hatch automatically.
Not a viable solution for 1958x but today we are talking about a few dollars in electronics and an electromagnet.
Not a viable solution today: the problem is not fridges in active use in houses, it's fridges in people's backyards/dumps/barns/whatever where they are no longer plugged into anything.
A battery could presumably power it long after being unplugged. But you're right - That article basically states that the problem was solved in 1958, by replacing the mechanical latch with a magnetic door. Coincidentally this research was from 1958, so I assume there is a connection there. Thanks for posting that - It puts thing into perspective.
You could probably use a single mic and a volume threshold, rather than a volume comparison with the outside, unless enough sound from the outside of the fridge gets to the internal microphone to set it off (e.g. during an earthquake or extremely loud party).
Not a viable solution for 1958x but today we are talking about a few dollars in electronics and an electromagnet.