Now, to consider installing a fan at the exhaust side of the chassis, the same fan model and faceplate examples were measured for sound pressure. Shown here, the sound pressure increase for the smallest spaced faceplate is less than half of what it was on the preceding slide. This illustrates that obstructing flow into the inlet has a more severe effect on increasing sound pressure. The same behavior is shown where a larger slit spacing and perforation design helps to reduce sound pressure increases.