Is it normal for my breasts to leak every time I hear a baby crying?

Yes. This is very normal. Everytime you hear your baby, (and in the beginning other babies!) it can stimulate release of the hormone oxytocin that causes let down of the milk in your breasts- leading to leakage. The more frequently you nurse the more attuned you will become to your baby's sounds and the less likely you will be to leak when around other babies.
Yes. Your let-down reflex is very strong - and totally normal.
Yes. It is common for a breast feeding mom to release milk (let down reflex) when she hears her baby, or even another baby, cry. This generally becomes less of a problem the longer you are nursing. It is caused by release of oxytocin in response to the baby cry. Wear absorbent breast pads in your bra when you need to to prevent milk leaking onto clothes.
Yes. Baby's crying stimulates areas of your brain that produce hormones which stimulate breast milk production. These same responses can be triggered in other ways (looking at a picture of your baby, thinking about the baby) that can be harnessed to achieve more productive pumping!
Yes. Absolutely, this is how it works! crying is one of the most powerful stimulants of breast milk production. In short - babies are supposed to cry - it helps breast milk production and is a healthy part of the cycle.
Yes. Yes it is. There is a natural response of let down with nursing moms when they hear a baby crying. The body knows that a hungry baby will cry and therefore wants to be ready to nurse as soon as you hear crying.
Yes. When a baby nurses, the milk "let-down" occurs only after your brain releases oxytocin, a hormone that prompts the milk ducts to contract. This hormone can be released whenever your body senses the baby is ready to nurse, whether she is suckling at the nipple, or just crying. Oxytocin can also make the uterus contract, which is why nursing mothers may feel contractions around the time they nurse.
Yes. This annoying event happens when many moms start breastfeeding. It typically becomes less of a problem as your breasts mature into making milk. Wearing bra pads (not plastic lined!) i learned that wearing patterned shirts helps hide leaks that get through the pad, since i hear crying babies all day at work!
Yes. Particularly if you recently gave birth. There are certain stimuli that cause the milk to let down. One is the anticipation of the baby's hunger which may be demonstrated by his crying.
Yes. Yes. It becomes a powerful reason to be sure everything you wear is wash and wear.....Much easier to clean. I couldn't add to all the great answers. This seems to be practical advice.