The speed of sound depends on the medium that the waves pass through, and is a fundamental property of the material. The first significant effort towards the measure of the speed of sound was made by Newton.
These meet ASTM safety standards and are suitable for most professions. Composite. Many safety boots are nonmetallic-instead of steel or aluminum, they are reinforced with a composite-material steel toe boots, usually made with thermoplastic polyurethane (TPU) or similar materials.
Safety Composite Toe Work Boots. No matter what line of work you are in, you need a pair of reliable shoes that gives you the stability to be on your feet. Some work conditions are more intense than others and require more durable shoes that are harder to weather. For those jobs we carry a wide selection of safety toe boots.