HOA fine fue to noise?

[Fernando Villasol]

I bought a condo 18 months agos rented ti same tenants that lived there the last 15 years. Las month the HOA sent me a notice of a violation due to exesive noise (the unit is occupied just by a 70 years old retired lady), I asked the tenant and she refused the charges and I informed the HOA. Last week they repited the violation and charged me with a fine of 25. I know there was some history with the neighbors below. Any advice on how to proceed? I am concerned about how to manage if this keep growing (do I need an attorney?)