For portable quiet cool mist humidifiers for study rooms, useful comparison points include placement, dimensions, power method, capacity, controls and the specific functions represented by the search.
Catalog options relevant to this combination include USB Mini Desk Humidifier, White Noise Humidifier for Peaceful, Comfortable Road Trips, and Compact Portable Car Humidifier and Relaxing Aromatherapy Essential Oil Diffuser. Their exact specifications can differ, so use the individual listings for final product details.