physics sound and waves

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Description and Tags

Physics

65 Terms

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wave
disturbances that transfer energy over a distance
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mechanical wave
wave that requires a medium in which to travel
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medium
any material; solid, liquid, or gas
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periodic motion
motion that occurs when the vibration, or oscillation, of an object is repeated in equal time intervals
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pulse
wave that consists of a single disturbance
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transverse vibration
occurs when an object vibrates perpendicular to its axis
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longitudinal vibration
occurs when an object vibrates parallel to its axis
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torsional vibration
occurs when an object twists around
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cycle
one complete vibration or oscillation
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rest position
position of the object before it moves or vibrates
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amplitude
distance from the equilibrium (rest) position to maximum displacement
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wavelength
distance between successive wave particles that are in phase
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in phase (same phase)
points on a periodic wave that have the same frequency and same displacement (from rest position) and moving in the same direction
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out of phase
points on a periodic wave that have the same frequency but not in phase
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180 out of phase (opposite phase)
points on periodic wave that have the same frequency and opposite displacement (from rest position) and moving in the opposite direction
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crest
high section of wave
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trough
low section of wave
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compression
region where the particles are closer together than normal
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rarefaction
region where the particles are further apart than normal
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audible sound wave
sound wave in the range of human hearing, 20Hz to 20kHz
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infrasonic wave
sound wave with a frequency below 20Hz
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ultrasonic wave
sound wave with a frequency above 20kHz
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echo
the sound energy reflected off a surface back to the producer of the sound
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Mach number (M)
the ratio of the airspeed of an object to the local speed of sound (airspeed/local speed)
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Loudness
describes how humans perceive sound energy; dependent on sound intensity
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pressure (p)
the force per unit area (F/A)
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sound intensity
the amount of sound energy being transferred per unit area; unit W/m^2
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decibel (dB)
the unit of sound level used to describe sound intensity level
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constructive interference
occurs when waves build on each other to make a larger wave
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destructive interference
occurs when waves diminish one another and create a smaller wave
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standing wave
wave that is created when waves travelling in opposite directions have the same amplitude and wavelength
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node
points that remain at rest
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antinode
points midway between the nodes where maximum constructive interference occurs
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supercrest
wave crest resulting from constructive interference
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supertrough
wave trough resulting from constructive interference
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first harmonic/ fundamental frequency
the simplest and lowest frequency standing wave
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second harmonic/ first overtone
the second lowest frequency standing wave
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third harmonic/ second overtone
the third lowest frequency standing wave
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resonance
the increases in amplitude of a wave (or vibration) due to the transfer of energy in phase with the natural frequency of the wave
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natural frequency (resonant frequency)
the frequency at which a medium vibrates most easily
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sympathetic vibration
the resonance of a mechanical or acoustical system at its resonant frequency by energy transferred from an adjacent system vibrating at this same frequency
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aeroelastic flutter
a wind induced vibration where the energy input from the wind equal or exceeds the energy lost due to damping, causing large (and potentially destructive) vibration
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acoustical resonance
resonance involving sound wave
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beats
periodic changes in sound intensity caused by interference between two nearly identical sound waves
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echolocation
the process of determining the location of objects through the analysis of echoes, or reflected sound
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pinna
* funnel for sound
* channels sound waves into the auditory canal
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auditory canal
* part of the external ear
* magnifies sounds in the frequency range of 1000Hz to 5500Hz by a factor of about 10
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tympanic membrane
* eardrum
* separates the outer ear from the middle ear
* tightly stretched, cone shaped membrane
* extremely sensitive
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Eustachian tube
* connects the cavity containing the middle ear to the mouth
* filled with air
* only opens when you swallow or yawn
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hammer, anvil, stirrup
* transmits the vibrations of the eardrum to the inner ear while magnifying the pressure variations by a factor of about 22
* three smallest bones in the body
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hammer/malleus
* the centre of the eardrum on the inner side is connected to it
* lever-like bone that rocks back and forth when the eardrum vibrates
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anvil/incus
* connected to the hammer
* vibration of the hammer causes it to vibrate
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stirrup/stapes
* transmits the eardrum vibrations to the start of the inner ear at the oval window
* when eardrum is pushed in by a compression wave, it pushes inward on the oval window
* when rarefaction is present in the outer ear and the eardrum is pushed outward, it pulls the oval window outward
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cochlea
* snail-shaped organ approximately 3cm long
* divided into two sections by the basilar membrane
* vibrations at the oval window cause pressure wavs in the fluid that fills it
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basilar membrane
* partition that divides the cochlea into two sections
* responds to different frequencies along its length
* when resonance is achieved, it will vibrate in one area which causes microscopic hairs in the area to vibrate
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semicircular canals
* three hard, fluid-filled loops in the inner ear
* right angles to each other
* act like accelerometers that help maintain the body’s balance by transmitting signals to the brain
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hearing aid
* worn behind the ear or in the auditory canal
* magnifies sound and directs it to the ear
* consists of a microphone and an amplifier
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outer ear
consists of the pinna and auditory canal
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middle ear
consists of the eardrum and three small bones: the hammer, the anvil, and the stirrup
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inner ear
consists of the cochlea and auditory nerve
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building acoustics
the total effect of sound produced in an enclosed or restricted space
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reverberation time
the time required for the loudness of the sound to drop by 60dB or until the sound is inaudible
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tsunami
an enormous sea wave or a series of enormous sea waves caused by an earthquake or other disturbance
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seismic waves
waves of energy that travel through earth
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buffet
a type of random vibration that is usually caused by an interruption of airflow