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