If you can hear it without a stethscope then it's pretty loud. But it could be the mucus etc. If the kid is wheezing, the sound is like heehee, like a motor or something.
I am no doctor but if I hear such sound I will rush to the doctor. And use ventolin for saftey purpose.
Different doctors tend to have different definition for asthma. Some said wheezing for below 6 is not asthma but allergy. Some said the same thing for below 3.
Honestly whether it's called asthma or not is just a terminology. We as parents of course don't like this term. Bottom line is if wheezing occurs once, we have to be more careful coz they can be recurring.