Put the complaints in writing and mail it to them. You are protected under California Civil Code Section 1927. Be mindful that this is a law that your complex has to adhere to. Also, know that not all things stated in a lease are enforceable or are limited to what is in the lease. The law supersedes. Everybody has a right to quiet enjoyment. If it is not quiet and the landlord does nothing, record it, have others witness it, call the building inspector to see if corners were cut with insulation, and sue in small claims. You can sue for the value of the apartment being less than fair market value related to noise and lack of enjoyment, all moving costs, emotional distress, etc.