Associated Home Owners of San Leandro

I live on Canyon Rd., the dead-end parallel to Wittier Rugby Field. They are currently playing intermural type sports (frisbee, etc.) late at night on the field - usually beginning at 8:00pm and ending at 10:00pm. The games are very loud with cheering and whistles being blown and I can't sleep! I've called to complain but am told that the Panoramic Hills Assoc. made a ''contract'' with UC around this issue allowing play until 10:00pm. I've been here 6 years, and never heard of this contract. The issue is becoming a major one as we have a 6-month old son who is awakened by the noise and we tired new parents can't catch any extra sleep either. Can someone help with this? Do I need to attend a meeting to complain? What can I do to have them stop or at least stop earlier? Thank-you!