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.
If the boots can withstand the 75 pound weight, they are labeled as I/75. The minimum impact rating for safety toe boots is I/50. The compression rating is the number of loads the shoes can withstand before cracking or breaking. For example, a C/75 will guard against compressive loads of up to 2,500 pounds.