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Chapter 12 Sound.

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Presentation on theme: "Chapter 12 Sound."— Presentation transcript:

1 Chapter 12 Sound

2 Section 1

3 Sound waves Compressional waves All sounds are caused by vibrations
formed when a vibrating object collides with air molecules, transferring energy to them Compressional waves have two regions, called compressions and rarefactions, which push air molecules together and then spread them apart

4 Medium the type of matter, whether liquid, solid, or gas; that sound waves travel through A sound wave’s speed depends on the substance of the medium and whether the medium is solid, liquid, or gas. Sound travels more quickly through solids and liquids because the individual molecules are closer together than the molecules in gas. As a medium’s temperature increases, its molecules move faster and it conducts sound waves faster.

5 Section 2

6 Properties of Sound Amplitude Intensity Loudness Decibel
The amount of energy a wave carries corresponds to its amplitude which is related to the density of the particles in the compressions and rarefactions. Intensity the amount of energy that flows through a certain area in a specific amount of time Loudness human perception of sound intensity Decibel Each unit on a scale that measures sound intensity

7 Infrasonic or subsonic waves
Pitch how low or high a sound seems to be Frequency is the number of compressions or rarefactions of a sound wave that pass per second human ears can hear frequencies from ~20 to ~20,000 Hz Ultrasonic waves sound frequencies over 20,000 Hz that have medical and scientific uses. Infrasonic or subsonic waves frequencies below 20 Hz usually can’t be heard but may feel like a rumble. Doppler effect change in pitch or wave frequency due to a moving wave source either the source of the wave or the observer can be moving

8 Section 3

9 Fundamental frequency Overtone
Music sounds that are deliberately used in a regular pattern Natural frequency frequency at which the a material vibrates Resonance the ability of a medium to vibrate by absorbing energy at its own natural frequency Sound quality differences among sounds of the same pitch and loudness Fundamental frequency the main tone played and heard Overtone vibration with a frequency that is a multiple of the fundamental frequency

10 Percussion instruments Beats
Musical instruments devices used to make musical sounds Strings instruments in which sound is produced by plucking, striking, or drawing a bow across tightly stretched strings Brass and woodwinds air vibration in a resonator with the pitch determined by the length of the vibrating tube of air Resonator Hollow chamber that amplifies sound Percussion instruments produce sound by being struck, shaken, rubbed, or brushed. Beats pulsing vibration in loudness

11 Section 4

12 Uses of sound Acoustics Echolocation Sonar Ultrasound waves
entertainment, warning signals, information Acoustics study of sound, which can prevent excessive reverberation and create good listening environments Echolocation process of locating objects by sending out sounds and interpreting the waves reflected back Sonar uses reflection of underwater sound waves to locate objects Ultrasound waves used to diagnose, monitor & treat many medical conditions Can produce images of internal structures for detection of medical problems Can treat medical problems such as kidney or gallstones

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