I think he probably is just highly sensitive to noise. Chances are he will get over it in a few months. Many years ago scientists discovered that a loud noise was one of the apparently instinctual fears of babies. Running the washing machine when he is asleep is not comparable to running the vacuum cleaner when he is awake. I guarantee you that my vacuum cleaner, which is old and very loud, would make him wail! You might try vacuuming while he is asleep and running the washer (which is not as loud) while he is awake. Perhaps the exposure to the washer, which is probably not too loud, will help habituate him to louder household machines.
Have you considered the possibility that it was not the crying of another child but the general excitement and confusion on your outing that elicited his crying? It is certainly a possibility. Even though he might enjoy being around children who are excited and making noise, formal planned movement activities might strain his tolerance just a bit.
Whenever he is in a setting likely to release his intense crying, make certain that you have handy a favorite comforting object—a pacifier, a bottle or a favorite toy to hold and manipulate. And concentrate on comforting, not scolding, as you try to help him calm down.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.