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P. Sci. Unit 6 Chapter 18 & 19 Sound and Light. Sound. Sound travels as longitudinal waves All sound is produced by vibrating objects. Sounds must have a medium to travel through (mechanical wave). Properties of Sound. The speed of sound waves depends on the medium it travels through.
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P. Sci. Unit 6 Chapter 18 & 19 Sound and Light
Sound • Sound travels as longitudinal waves • All sound is produced by vibrating objects. • Sounds must have a medium to travel through(mechanical wave)
Properties of Sound • The speed of sound waves depends on the medium it travels through. • Two properties that affect the speed are temperature and density.
Loudness(intensity) Depends • on your distance from the source. • on the energy of the wave • the greater the amplitude – the more energy carried – the louder the sound.
Relative intensity is found by comparing a sound with the quietest sound a person can hear. It is measured in decibels (dB) 0 dB – 120 dB quietest sound – threshold of pain
Pitch • How high or low a sound is. • It is determined by the frequency of the sound wave. • High frequency =high pitch sound Low frequency = low pitch sound
Human Hearing • The human ear can hear sounds from 20 Hz to 20,000 Hz. • Infrasound – any sound with a frequency below human hearing. • Ultrasound – any sound with a frequency above human hearing.
How we Hear • The ear converts vibrations in the air (compressional waves) into nerve impulses that travel to the brain.
Sonar • Sonar systems determine distance by measuring the time it takes for sound waves to be reflected back from a surface. • d = v x t d = distance t = time of reflection v = average speed of sound waves in water
Ultrasound reflection • Ultrasound waves (between 1 – 15 million Hz) are used to produce sonograms (computerized images) • Used to view organs inside the body without having to perform surgery.
Review • What does the speed of a sound wave depend on? • What is Pitch determined by? • How is relative intensity found? • How do we use sound reflection?