Acoustical design services design rooms, buildings, and other structures to optimize sound quality. They consider factors such as room dimensions and shape, the position of speakers and listeners, the placement and types of doors, and the placement and types of windows or skylights. Acoustical design services pay special attention to the reflection of sound waves in their selection of suitable acoustic materials. Companies may also offer services such as acoustical field testing, sound dampening, mechanical noise control, noise and vibration measurement and monitoring, and environmental noise control and analysis. Acoustical design services may also manufacture and install custom acoustical products such as curtain systems, baffles, pipe wraps, metal enclosures, barrier walls, removable panels, backless panels, fabric-covered panels, and portable screens.