# SOUND Chapter 11.

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SOUND Chapter 11

Review Terms Compression Rarefaction Longitudinal wave Medium
Wavelength Amplitude Frequency Interference

New Things: Lesson 1 Sound wave: Vibration longitudinal wave
Can only travel through matter Vibration Rapid back-and-forth movement that can occur in matter (S, L, G) ie: guitar string being pulled causes a disturbance in the air. There is energy in this disturbance that is carried outward from the source = sound wave

What Affects the Speed of Sound?
1) Density/stiffness of the medium How closely particles are packed together Temperature of the medium Inc temp = Inc speed of sound FOR GASES Why? Inc in energy in particles = more energy transferred Dec temp = Inc speed of sound FOR LIQ & SOLIDS Why? Dec in temp = particles closer together = faster for sound to travel throughout the medium

New Things, Lesson 2 Doppler effect: Intensity:
Change of pitch when a sound’s source is moving in relation to an observer Source of sound is moving; observer is standing still Intensity: Amount of sound energy that passes through a square meter of space in 1 second

More New Things: Lesson 2
Pitch: Perception of how high or low a sound seems Resonance: Increase in amplitude that occurs when an object vibrating at its natural frequency absorbs energy from a nearby object that is vibrating at the same frequency (1 ball of play-doh is added to an equal ball of play-doh to create a larger ball of play-doh)

Detecting Sound 1 Outer Ear Middle Ear Collects sound
Ear canal – directs collected sounds to middle ear Middle Ear Amplifies sound Eardrum – sounds from outer ear cause eardrum to vibrate; vibrations transfer to 3 bones: Hammer Anvil Stirrup These bones conduct sound towards inner ear

Detecting Sound 2 Inner Ear
Turns sound waves into signals that can be recognized by the brain Cochlea – small, fluid-filled chambers Sound passing through cochlea causes tiny hair-like cells to vibrate; movement of these cells produces nerve signals; signals travel to brain; signals interpreted as sound.

Decibel Scale dB Describes the intensity (loudness) of a sound

Relationship btwn vocab terms
Frequency & wavelength Longer wavelength = lower frequency Shorter wavelength = higher frequency Pitch & Frequency Higher frequency = higher pitch Lower frequency = lower pitch

Sound Interference Constructive Destructive Beats

Beats How to calculate beats: The difference in frequencies
ie: a musician plays a note with a pitch of 400Hz; another musician plays a note with a pitch of 395Hz; the difference is 5 Hz; beats will occur 5 times per seconds

Fundamental & Overtones
Fundamental – lowest frequency that a material naturally vibrates Overtones – higher frequencies at which the material vibrates Timbre (TAM-bur) – caused by the interferences of these waves, unique to each instrument; differences in the number and intensity of fundamental/overtones.

Deafness Conductive and Nerve Temporary: Wax, foreign obj, excess mucus, infection, drugs Permanent: Hereditary, genetic, prenatal exposure to disease, loud noise, trauma (ie: ruptured dear drum), diseases, exposure to chem, etc

Review Things, Lesson 3 Transmission – movement of sound waves through a medium Absorption – transfer of energy by a wave to the medium through which it travels Reflection – bouncing of a wave off of a surface

New Things 1, Lesson 3 Echo – reflected sound
Reverberation – collection of reflected sounds from the surfaces in a closed space Acoustics – study of how sounds interact with structures *Fun Fact* Designing a space: Engineers design different rooms to reflect sound in different ways. The shape/contour of the walls and other structures in the room, as well as the materials they’re made of, reflect sound differently. ie: a concert hall vs a classroom vs a recording studio

New Things 2, L3 Echolocation – use of reflected sounds to locate objects Sound wave is sent out; some of the sound is reflected back Sonar – Sound Navigation and Ranging – use of reflected sound waves to locate underwater objects A sound wave is sent out into the water; as the sound wave goes deeper into the water, the wave spreads out in a cone/beam; when the wave strikes something, it is reflected back to the source of the wave

New Things 3, L3 Ultrasound – sounds that have a higher frequency than humans can hear (imaging, treatment) Uses of ultrasound: Imaging: High-frq sound waves emitted; muscle, bone, tissue, fat, all reflect waves at different rates. Based on these reflections, and image can be created (sonogram) Medical treatment: Ultrasound therapy – high-frq sound waves emitted; the vibrations act like a massage for those muscles/tissues deeper in the body

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