A rubber sheet commonly finds use in motor and marine applications given that it works as an effective sealant against liquids, sounds, and mechanical vibrations. You can find rubber sheets in varying thicknesses, with thicker variants offering better insulation.
A neoprene rubber sheet comes in black, while silicone rubber sheets come in a multitude of colour options. Silicone sheets also tend to offer better operational temperature ranges. Think carefully about whether you should choose DIY or professional installation.