The outer ear acts like a funnel to direct sound waves from the air to the tympanic membrane (eardrum). Sound causes the tympanic membrane to vibrate. These vibrations cause the three bones in the middle ear (Malleus, Incus, Stapes) to move mechanically. The middle ear sends these mechanical vibrations to the inner ear, where they are picked up by tiny hair cells (Cilia) and sent as electrical impulses along the auditory nerve to the brain.
DECIBLES
The decibel (dB) is used to measure sound level, but it is also widely used in electronics, signals and communication. The dB is a logarithmic unit used to describe a ratio. The ratio may be power, sound pressure, voltage or intensity or several other things. Each increase of 10 on the dB scale represents a tenfold increase in loudness. 20 dB is 10 times as loud as 10 dB, 30 dB is 100 times louder than 10 dB, and so on.
When you notice a difference between loud sounds and quiet ones, your ears are perceiving changes in sound pressure level. Intensity (or volume) is measured in decibels (dB). Zero (0) dB is the softest sound that can be heard. Normal conversation is around 40dB to 60dB, a whisper around 30dB. A rock concert can average between 110 and 120 dB. The sound from a jet plane is approximately 140 dB. Pain from hearing is subjective. Levels below 125 dB may be painful to some individuals. At rock shows, the dB level can be as great as 140 dB in front of the speakers, but less than 120 dB at the back which is still very loud and dangerous.
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