A sound blocking level of STC 40 can provide privacy between rooms if the speech level is no louder than general conversation. Once speech levels rise, phrases and sentences can be understood in adjacent rooms and will likely disrupt people. Acoustic standards, guidelines and building rating systems occasionally permit an STC rating as low as 40. However, most require blocking levels of STC 45 or higher1. An STC 40 level of blocking should be considered a minimum as privacy cannot be achieved at levels below STC 40.