What is the layer of cotton laid under the car called?

[StLuna]

The layer of felt is called chassis soundproofing cotton. Here is some relevant information: 1. Introduction to soundproofing cotton: Soundproofing cotton has excellent thermal insulation properties. When applied inside the car's engine hood, it effectively prevents the engine's high temperature from directly transferring to the hood, thereby protecting the hood's surface paint and avoiding fogging on the hood during rainy days, which can affect visibility. 2. Functions: After soundproofing the doors, the hollow cavities inside the doors are effectively filled, making the sound of closing the doors softer. After soundproofing the front and rear hoods, firewall, and floor, the engine's loud valve noise is filtered out. During low-speed driving, most of the tire and road noise is suppressed, with some room for further improvement at higher speeds. The vehicle's stability is significantly increased, and the shock absorption and cushioning performance are noticeably enhanced. It also reduces and effectively alleviates metal fatigue in the chassis, extending the vehicle's lifespan.