The speeds of light, which is the electromagnetic wave, and sound, which is a mechanical wave, are two very different finite numbers. Light moves much faster, 186,000 miles per second, while sound is measured at around 700 miles per hour, which is significantly slower. Light waves are much shorter, which means they are easier to deflect. Sound waves are much longer, and tend to diffract, or bend around obstructions. The longer the wavelength, the easier it is to diffract, or bend around barriers or obstructions that try to get in the way. That is why you can not see someone until they actually enter the room, but you can hear them walking down the hallway that is adjacent to the room. Our eyes measure the light that enters them, but our ears measure the sound waves that are collected by them.