What's your definition of excessive noise RE:kids running around in an upstairs apt?

[Tom Maurer]

An upper apartment in the building I own has hardwood floors with a great tenant. The tenant in the one below it (another great tenant other than this constant complaint) complains that, when the tenant in the upper apartment has her grandkids over they constantly run back and forth between one of the bedrooms and the living room. They come over for about 3 hours 3 times/week never past 9:30p. I’ve talked to the upper tenant and she got a throw rug for the hallway and part of the living room. That didn’t help. The lower tenant claims that, if I don’t stop the unreasonable noise I am violating the lower tenant's “right to the quiet enjoyment” of his property. I asked my manager to go & check out the noise when it happens. He asked the question….what is excessive noise? Any thoughts on this?