Transmission loss predictions are based on the diameter of the pipe, pipe thickness, pipe material, and fluid inside and outside of the pipe. The internal pulsations (transverse modes) must be predicted prior to using a pipe TL model. Transmission loss models for pipes also tend to include the “ring frequency” which is typically defined as the first mode (breathing/hoop mode). In most TL models, the lowest transmission loss occurs at or close to the ring frequency. A low TL means that more noise can escape through the pipe wall and into the environment. The TL loss will tend to increase for frequencies larger than the ring frequency and those smaller than the ring frequency.