Instead of trying to find an electrical outlet, or bothering others with motor noise, a manual breast pump allows you to pump quickly and quietly, wherever you are! (geekwrapped.com)
Motor Noise Level — Although the noise level of the pump motor may not be the most important aspect of the pump, it may be a feature that you are concerned about especially if discretion is important to you. (breastpumpcomparisons.com)
While the Graco DuetSoothe Infant Swing + Rocker has a range of speed and fleshed out with a couple of soothing nature sounds, it does suffer from a lackluster mobile and a clicking motor noise which might effect smooth sleeping of the baby. (babygearspecialist.com)