Chapter 20: Sound Flashcards
Sound is a variation of
The pressure of a medium
Sound is a typically of
Air
Sound propagates as a
Longitudinal pressure wave
Sound travel at a speed characteristics of
The medium in which it propagates
Sound is our ear are devices which
Detect sound
Sound is a form of
Energy that exist whether or not it is heard
Most sounds are waves produced by
The vibration of matter
The vibrating material then sends a disturbance through the surrounding medium, usually air, in the form of
Longitudinal sounds waves
Under ordinary condition, the frequencies of the vibrating source and sound waves are
The same
The subjective impression about the frequency of sound is called
Pitch
The ear of a young person can normally hear pitches corresponding to the range of frequencies between about
20 and 20,000 Hertz
Sound waves with frequencies below 20 Hertz are
Infrasonic (frequency too low for human hearing)
Sound waves with frequencies above 20,000 hertz are called
Ultrasonic (frequency too high for human hearing)
Human cannot hearing the two different types of sounds, what was that?
Infrasonic and ultrasonic sound
Sound waves are
Vibrations made of compressions and rarefraction
Sound waves are (2)
Longitudinal waves
Sound wave requires
A medium
Sound wave travels through
Solids, liquids, and gases
The wavelength of sound were the distance between
Successive compressions or rarefactions and both of them travel at the same wave speed
Medium that transmit
Sound
Any elastic substance - solid, liquid, gas, or plasma can
Transmit sound
In elastic liquids and solids, the atoms are relatively
Close together, respond quickly to one another’s motions and transmit energy with little loss
Sound wave about 4 times faster in water than in air and about
15 times faster in steel than in air
Speed of sound in air depends on
Wind conditions, temperature, humidity
Speed in dry air at 0 degree Celsius is about
330 m/s (738 mph) and in water it is vapor slightly faster and in warm air faster than cold air
Each degree rise in temperaure above (0 degree Celsius), speed of air increases by
(0.6 m/s) or 0.6 T
Reflection
Process in which sound encountering a surface is returned
Reflection often called an
Echo
Multiple reflection called
Reverberations
Reflection of the sound reflects from a
Smooth surface the same way that light does
Angle of incidence equals to
Angle of reflection
If the reflective surface are too
Absorbent, the sound level will be low and the room will sound dull and lifeless
Reverberations are best heard when you sing in a room with
Hard-surfaced walls
Accoustic
Study of properties of sound
Some have reflectors to
Direct sound which also reflect light so what you see is what you hear
Refraction
Bending of waves caused by changes in speed affected by wind variations and temperature variations
Sound does not always travel in
Straight line paths
Sound bends from warmer (less dense) air to
Cooler (denser) air
When air near the ground on a warm day is warmed more than the air above, sound tends to bend
Upward
In the evening, when air directly above a pond is cooler than air above, sound across a pond tends to bend
Downward
Ultrasound
Multiple reflection and refractions of high frequency sound waves
Ultrasound devices sends
High-frequency sounds into the body
Wave reflects more strongly from the exterior of the organs, producing an
Image of the organs
Ultrasound used instead of X-ray by physician to
See the interior of the body
Dolphin emit ultrasonic waves to enable them to
Locate object in their environment
Forced vibration establishing in an object by
A vibrating force
If we hold a tuning fork against a table after striking it, the sound is
Louder because the table is forced to vibrate, and with its larger surface area, the table sets more air in motion
A frequency or a set of frequencies at which an object preferentially vibrates determined by
Elasticity of the object and the shape of it
A phenomenon in which the frequency of forced vibrations on an object matches
The object’s natural frequency
Interference is a property of
All waves and wave motion
Interference: Superposition of waves that may
Either reinforce (add) or cancel each other (subtract)
Two patterns of interference
1) Constructive interference
2) Destructive interference
Constructive interference increased amplitude when
The crest of one wave overlaps the crest of another wave
Destructive interference reduced amplitude when
The crest of one wave overlaps the trough of another wave
Beat is a
Periodic variations in the loudness of sound due to interference
Beat occur with any kind of
Wave
Beat provide a comparison of
Frequencies
The interference of two sound sources of slightly different frequencies produces
Beats
