The malleus, incus and stapes (otherwise known as the hammer, anvil and stirrup) are the smallest bones in the human body and are full size at birth. All three together could fit on a penny. The whole area of the middle ear is no bigger than an M&M. The cochlea (inner ear) is about the size of a pencil eraser. The ear never stops working, even when people are asleep. The ear continues to hear sounds, but the brain shuts them out. Ears are self-cleaning. Pores in the ear canal produce cerumen, or ear wax, and tiny hairs, called cilia, push the wax out of the ear. Sound travels at the speed of 1130 feet per second, or 770 miles per hour. A sonic boom occurs when an object breaks the speed of sound. The sound waves from behind and in front of the object crash into each other and create the boom. Chuck Yeager was the first American pilot to travel faster than the speed of sound. At 115 dB, a baby's cry is louder than a car horn. In Africa, a tribe of people call Maabans live in such quiet that they can hear a whisper from across a baseball field, even when they are very old. The hearing of a dog is more sensitive than humans. Dogs can hear much higher frequencies, which is why they respond to "silent" dog whistles. More than 28 million Americans have a hearing loss. More than 1/3 of the U.S. population have a significant hearing impairment by age 65. Approximately 2 million people are profoundly deaf. One of every 1,000 infants is born totally deaf. Sitting in front of the speakers at a rock concert can expose a person to 120 dB, which will begin to damage hearing in only 7-1/2 minutes. It does not matter if you like the sounds you are exposed to. An orchestra playing Mozart at 120 dB will damage your hearing as quickly as Metallica playing at 120 dB. Two out of three babies will have an ear infection before age 1.
