[PHY] Chapter 15 - Sound

DARRELL ER (COPYRIGHTED) © TOPIC 15: SOUND DARRELL ER (COPYRIGHTED) ©

CHAPTER ANALYSIS THE ABOUT MASTERY EXAM WEIGHTAGE DARRELL ER (COPYRIGHTED) ©

SOUND WAVES SPEED OF SOUND IN MEDIUM ECHO KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

SOUND WAVES Sound waves are propagated as longitudinal waves whose particles vibrate parallel to the wave motion direction. Sound waves are mechanical waves, as they require a medium to travel. The source of a sound wave is by a vibrating source. It can be produced by vibration of objects, eg drum, tuning fork, vocal cords. SOUND WAVES DARRELL ER (COPYRIGHTED) © When vibrating object alternately pulls or pushes on the layers of air adjacent to it, it causes small but rapid changes in air pressure. Compressions are regions where particles are pushed closer together, resulting in higher pressure. Rarefactions are regions where particles are pulled further apart, resulting in lower pressure.

SPEED OF SOUND IN MEDIUMS Sound travel faster in denser mediums as energy is transferred more quickly between particles. Hence, sound travel fastest in solid > liquid > gas. *Sound does not travel in a vacuum. SOUND WAVES DARRELL ER (COPYRIGHTED) © Medium Speed / ms-1 Vacuum 0* Air 330 Water 1500 Steel 5200

ECHO When a sound wave is reflected by a large, hard and smooth surface, an echo is produced. ECHO DARRELL ER (COPYRIGHTED) © Speed of sound = = Distance Time Distance by echo to surface & back Echo Time

PITCH & LOUDNESS C.R.O ULTRASOUND KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

PITCH & LOUDNESS Loudness is measured by amplitude & is a measure of the amount of energy carried by the sound. Pitch depends on the frequency (number of waves formed in 1s). CATHODE RA Y OSCILLOSCOPE DARRELL ER (COPYRIGHTED) © Used for displaying waveforms. Y axis – voltage (amplitude) X axis – time (frequency)

ULTRASOUND An ultrasound is a type of sound wave that is above 20kHz. Human audible frequency is between 20Hz and 20kHz. ULTRASOUND DARRELL ER (COPYRIGHTED) © Ultrasound allows imaging because of the difference in time taken for the waves to return from different depths of the medium. Application: - Pre-natal scanning - Sound navigation and ranging (sonar) to measure distances in air or water - Quality control in manufacturing - detector monitors strength of ultrasonic signals

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