Quiet enjoyment is an "implied covenant" between a property owner or landlord and their tenants. Quiet enjoyment is not a promise of absolute silence in one's rental. Instead, it's a loosely defined principle that protects you from disturbances — of all sorts, not just noise — that make a unit uninhabitable.
You might be wondering if your lease agreement includes a clause that promises you "quiet enjoyment" while living in your home. However, since quiet enjoyment is an implied covenant, it's understood to be applied to all rentals, regardless of whether it's explicitly stated.
When you rent a unit, the landlord has to provide you with a place that's actually habitable, without anything that would seriously disrupt your quiet enjoyment.
Obviously, quiet enjoyment is going to be a subjective standard, largely depending on where you live. Someone renting a house on a farm in the middle of rural Oklahoma would have a much different sense of "quiet enjoyment" than someone renting in the heart of Manhattan.
For this reason, there's no legal definition of quiet enjoyment, as violations of the covenant are determined by a drastic disturbance to the housing experience that one could reasonably expect. There are, however, a few standard violations that will almost always constitute quiet enjoyment:
Since peaceful enjoyment is so subjective, there isn't an official body to report to or legal means of taking action against a property in violation. The best course of action for tenants is to address the situation directly if they feel safe doing so, either with the property owner, tenant or outside party that's creating the disturbance.