"in recent years@ plastic gears have found their popularity as replacements for metal gears in selected@ lightly loaded applications. Many studies have been done in the area of plastic gearing such as plastic material selection@ injection molding and load capacity of plastic gears. Severai historical papers imply that plastic gears are ""quieter"" than steel gears. Yet@ there have been few studies that focus on studying the transmission errors of plastic gears and relating these errors to the noise that is generated. This paper focuses on the transmission error and sound pressure level measurements of several plastic gear sets and compares experimental static transmission error measurements to computer predictions. Based on the experimental results@ in plastic gears the tooth contact is more susceptible to occurring off the line of action due to excessive tooth deflection. This directly affec?s the transmission error behavior. A computer program that considers off line of action contact is used to accurately predict static transmission error for the experimental plastic gears. According to previous studies on metal gears@ there is a correlation between mesh harmonics of transmission error and sound pressure level. This study presents results used to check this correlation in plastic gears. The comparison of the ratio of sound level to transmission for the plastic gears and steel gears with similar overail geometry specifications is also presented."