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509-513 in your Text Define sound. What part does each of the following play in allowing you to hear sound: outer ear, middle ear, inner ear? Sound Notes and The Ear - sound - a disturbance that travels through a medium as a longitudinal wave. The ear consists of three basic parts - the outer ear, the middle ear, and the inner ear. Each part of the ear serves a specific purpose in the task of detecting and interpreting sound. Outer ear - Sound waves are gathered by the outer ear made up of the ear, the ear canal, and the eardrum. The outer ear is shaped to help capture the sound waves (energy transferred in particles of air) and send them to the ear canal, which transfers them to the eardrum. The vibrations of air particles cause the eardrum to vibrate. Middle ear - The middle ear amplifies sound waves. Inner Ear - The inner ear transmits vibrations from the bones of the middle ear to the liquid in the inner ear. The tiny hairs in the inner ear vibrate as the liquid vibrates. The vibrating tiny hairs transmit the energy to nerves attached to the hairs. The nerve impulses are transmitted to the brain for connections in the brain for understanding of the sound as “hearing.” Explain how sound is made by a drum, guitar or your voice. *Examples of how sounds are made: drum - as drum is struck, drumhead moves in and then out creating compressions and rarefactions. guitar - as guitar string is plucked it vibrates back and forth creating vibrations, which create compressions and rarefactions. vocal cords - as you speak air is pushed up from the lungs across the two folds of tissue, the vocal cords, causing vibrations and then compressions and rarefactions. Why can no sound be heard in space? What affects how loud a sound is? What unit is used to measure it? What is the range of human hearing? What are sounds beyond this range called? What is pitch? Give an example of how pitch can be changed. * Sound can only travel if there is a medium, which is why no sound can be heard in space. - loudness - greater energy = greater amplitude = greater intensity = louder sound. Measured in decibels (dB). Each 10 dB increase means an increase of ten-fold in intensity. Sounds louder than 85 dB can cause pain and hearing loss. * frequency is changed by muscles in the throat, affecting the pitch of the voice. The higher the frequency, the higher the pitch. Most people can hear frequencies between 20 and 20, 000 Hz. Sounds of a higher frequency of 20,000 Hz are called ultrasound. Those below 20 Hz are called infrasound. - pitch - the description of how high or low the sound seems to a person. (pianos have a range of 27 - 4,186 Hz) Summaries