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.
Make sure the ball of your foot lines up with the the ball of the boot (that's the widest part of the boot where the steel shank ends). If the boot is too short, your toes will be forced into the toe box. Boots should slip slightly in the heel.