Shaker injections support the hypothesis that the 52 Hz peak from the HVAC chilled water pump is coupling through the cryopump manifold baffle at EX. The attached spectrum shows a 50 Hz sinusoidal injection of a shaker in red, shaking the vacuum enclosure around the crypump manifold baffle, which also shows up in the PEM channels. Using this injection to calculate the vibrational coupling factor to DARM, and then multiplying by the magnitude of the 52 Hz HVAC peak in the PEM channels, results in an expected contribution to DARM within about 75% magnitude of the observed 52 Hz peak in DARM. We consider power coupling functions good to a factor of 2, so 75% is reasonable.