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Sound Part 1: Sound Waves Recall There are two major categories of waves. Mechanical Waves that transfer energy through matter. Electromagnetic Waves that transfer energy through a field. They require a substance (a medium) to travel through. They do NOT require a substance (a medium) to travel through. e.g. water, sound, seismic waves e.g. light, radio, ultraviolet, x-rays What Are Sound Waves Sound waves are created when an object vibrates. When an object vibrates, it creates longitudinal waves. Properties of Sound Waves Sound waves have 3 main properties. 1. Speed How fast the sound wave moves in a medium. 2. Loudness How intense the sound is. 3. Pitch The frequency of the sound wave. 1. Speed The speed of sound depends on the medium. Sound waves travel faster through more dense mediums. more dense Gases Liquids Solids 769 mph 1400 mph 5000 mph 1. Speed Table: Speed of sound for different materials less dense more dense Dry Air 331 mph Fresh Water 1509 mph Salt Water 1546 mph Lead 1210 mph Iron 4480 mph Aluminum 5170 mph 2. Loudness Loudness is how intense the sound is. The intensity of a sound is a measure of how much energy the sound wave has. The amplitude (height) of a sound wave shows its loudness. 2. Loudness lower amplitude higher amplitude less energy more energy SOFTER LOUDER! 2. Loudness Loudness is measured in decibels (dB). The decibel scale measures sound intensity. A 0 db sound can barely be heard. A 100 db sound can cause hearing loss. Interactive Loudness Scale 2. Loudness of Different Sounds Threshold of hearing 0 db Whisper 15 - 20 Normal conversation 40 - 50 Street noise 60 - 70 Rock concert 110 - 120 Threshold of pain 120 Jet take off 120 - 160 3. Pitch Pitch is how high or how low a sound is. The frequency of a sound wave determines the pitch of the sound. The wavelength of a sound wave shows its frequency. 3. Pitch 1 sec. 1 sec. lower frequency higher frequency lower pitch higher pitch e.g. tuba e.g. flute Music vs. Noise Music and noise are different. It depends on the shape of the sound wave. Noise Music No clear pattern A clear pattern Timbre No two types of instrument sound the same, even when playing the same note! This is because each instrument makes its own unique pattern of sound waves. The particular sound that an instrument or human voice has it called its timbre (TAM-buhr). Timbre No two types of instrument sound the same, even when playing the same note! This is because each instrument makes its own unique pattern of sound waves. Review! A B C D Which of the sound waves has the... Highest volume? Lowest volume? Highest pitch? Lowest pitch? Any Questions? Sound Part 2: The Ear Introduction Ears are sense organs that respond to sound. Your ear converts sound waves into electrical signals that your brain interprets. The ear’s structure is designed to receive and transmit the sound waves… Parts of the Ear The ear is divided into 3Ear major sections: The Outer Contains the pinna, ear canal and ear drum The Middle Ear Contains three bones: hammer, anvil & stirrup The Inner Ear Contains the cochlea and auditory nerve Parts of the Ear Outer Ear Middle Ear Inner Ear anvil pinna hammer stirrup ear canal cochlea ear drum auditory nerve The Outer Ear The Outer Ear The Outer Ear The pinna is specially shaped to gather and focus sound waves and direct them into the ear The ear canal is a hollow tube that carries the sound waves to the ear drum The sound waves hit the ear drum, causing it to ` vibrate. The ear drum transmits these vibrations into the inner ear where they are amplified The Ear Drum The Middle Ear The Middle Ear The Middle Ear Has the smallest bones in the human body: the hammer, anvil and stirrup Their job is to amplify the vibrations of the ear drum and transmit it into the inner ear The stirrup “taps” on the inner ear at a ` spot called the oval window Stirrup Inner Ear Bones Ham me r Inner Ear Bones The Inner Ear The Inner Ear The Inner Ear The cochlea is a snail-shaped tube that is lined with receptors that respond to sound The receptors are tiny hair cells that shake back and forth in response to sound waves When they shake, the hair cells create ` electrical signals called nerve impulses which go to the brain along the auditory nerve The Cochlea Hair Cells Analogy for Inside the Cochlea A seagrass meadow High vs. Low Sounds High pitch sounds carry more energy and travel further into the cochlea Lower pitch sounds carry less energy and don’t travel as far into the cochlea A Final Look! Outer Ear Middle Ear Inner Ear The Main Idea § The ear is divided into 3 sections: the outer ear, middle ear and inner ear. § At the outer ear, sound waves are focused by the pinna down the ear canal to the eardrum. § The sound waves make the eardrum vibrate. § The vibrations are amplified by the 3 middle ear bones: the hammer, anvil and stirrup. § The stirrup transfers the vibrations to the cochlea within the inner ear. § The vibrations activate hair cells inside the cochlea, which send electrical signals to the brain along the auditory nerve. § The brain interprets these signals as sound. Any Questions?