The use of composite materials for reducing weight in structures sometimes leads to a surprising and disappointing increase in noise and vibration levels. This paper presents a comparison of the acoustical performance of six panels with different material properties. The comparison was carried out using a Statistical Energy Analysis (SEA) model of a sound transmission loss test facility. The six panels were individually evaluated, and the noise due to acoustical and structural excitation of each panel was predicted. The results indicate relationships between noise and the physical properties of the panels, and demonstrate that the use of composites has given the designer more flexibility in the noise control design of structures. Composites allow substantial decreases in weight while maintaining stiffness, two properties which can affect the noise behavior of a panel considerably. Designing with regard to weight and stiffness and their effect on noise can aid in avoiding unexpected noise problems at a later time.