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163 Cards in this Set
- Front
- Back
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what are the physical properties of sound?
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frequency, intensity, time
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How do humans percieve sound?
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pitch, loudness, localization
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The source of a sound must be able to ___________
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vibrate
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To vibrate a source must have what two properties?
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mass and elasticity
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To transmit sound, a medium must be capable of _____________
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being set into vibration
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What two properties must a medium have to be set into vibration?
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mass and elasticity
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mass
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- the ammount of matter present
- applies to gases, liquids and solids |
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elasticity
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property that enables recovery from distortion of shape or volume
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when a medium is very elastic sound travels much _________
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faster
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The tendency of air volume to return to its former volume after compression is due to what?
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elasticity
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is sound a longitudinal or transverse wave?
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longitudinal
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what two opposing forces cause vibratory motion to occur?
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inertia and elasticity (the interaction between them)
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density increases (crowding)=
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compression
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density decreases (thinning)=
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rarefaction
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what happens with the movement of air mass?
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alternate regions of compression and rarefaction move throughout medium. The medium is not displaced over a great distance. A wave of disturbance moves through the medium.
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sound is characterized by what?
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propagation of density changes through an elastic medium
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sound is defined as what?
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the transfer of energy through an elastic medium.
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air mass offers ________ to energy transfer
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resistance
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kinetic energy is transformed to _________ energy
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thermal (heat)
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free vibration
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no additional energy is applied to the system. Damped pattern of vibration.
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forced vibration
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additional energy is applied to the system, reduces frictional resistence effects
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resonance
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property of system oscillating at a particular frequency with minimum dissipation of energy
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frequency
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the rate of vibratory motion, the number of "cycles per second". Measured in hertz.
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what defines one cycle?
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movement from equilibrium to maximum displacement in one direction, back to equilibrium, on to max displacement in opposite direction, then back to equilibrium
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period (t)
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the time required to complete one cycle, "seconds per cycle"
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what is the equation for period (t)?
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T= 1000/F
F= frequency |
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what is the equation for frequency (f)?
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F= 1000/T
T=period |
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frequency of vibration of the source is determined by properties of __________
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the source
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frequency of vibration of air particles is the same as ____________
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the source
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speed of wave propagation is determined by properties of ___________
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the medium
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the speed of sound transmission is ___ times greater in water than air and in steel it is ______ times greater than that of air
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4, 14
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frequency and period are __________ related
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inversely
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impulse wave shapes
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single burst of one or several pulses
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oscillatory wave shapes
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alwayus have a definate repeating shape. Can be complicated, but it is always repeated.
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sinusoidal wave shapes
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have a simple repeating shape. A pure tone is sinusoidal.
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simple harmonic motion
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motion is similar to a spring or pendulum. Molecules move at a specific frequency related to properties of the source that set it into vibration. Move until friction inherent in medium slows the motion.
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what is another name for simple harmonic motion?
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sinusoidal motion
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sinusoidal vibrations are the _________ of all vibrations and hence all possible sounds
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buiulding blocks
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the waveform
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a plot in change in amplitude of displacement over time
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what are the five dimensions of a sine wave?
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- frequency
- period - amplitude - phase - wavelength |
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instantaneous amplitude
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you can measure this at any point along the waveform
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maximum amplitude
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highest positive value
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peak to peak amplitude
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max distance between the highest and lowest amplitude
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phase
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defines the angle in degrees at the moment rotation begins
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wavelength
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relates frequency and speed of sound, it is the distance traveled during one period
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wavelength _________ as frequency increases
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decreases
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as speed of sound increases wavelength __________
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increases
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with regard to phase, maximum amplitude is always what?
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90 degrees
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with regard to phase, maximum negative displacement is always what?
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270 degrees
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all waves that are not sinusoidal are _________
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complex waves
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complex waves are __________ added together
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simple sinusoids that can differ in amplitude, frequency and phase
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fourier analysis
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all complex waves can be classified by reference to:
1. is periodicity present? 2. how complex is the wave? |
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periodic waves
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wave that repeats itself over time
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sinusoidal components cannot be selected at random. Instead they must what?
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satisfy a harmonic relation
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harmonic relation
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each sinusoid in the series must be an interger multiple of the lowest in the series.
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square waves
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each component is an odd integer multiple of fundamental frequency
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sawtooth wave
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components are odd and even integer multiples of the fundamental frequency
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aperiod wave
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lacks periodicity, vibratory motion is random.
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amplitude spectrum
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an alternative way to graph the waveform. Shows amplitude as a function of frequency with vertical lines.
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octave
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doubling of the frequency
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what is one octave below 1000?
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500
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What is one octave above 250?
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500
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line spectrum
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energy only at frequencies identified by vertical lines
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continuous spectrum
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energy present at all frequencies between certain frequency limits
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phase spectrum
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defines starting phase as a function of frequency
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what is the largest tolerable intensity for the human ear?
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10 to the power of 12 intensity units
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what do we use to describe the dynamic range of the auditory system?
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logarithms
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the bel
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log scale to the base 10
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what is the range of human hearing in bels?
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12 bels
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what is the range of human hearing in dB?
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120 dB
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what is the log of 2
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.3
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reference point for intensity level
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10 ^ -16 watts/cm ^2 (ten to the negative sixteenth watts per cm squared)
OR 10^ -12 watts/m^2 |
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pressure is what?
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force/unit area
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what is the unit of measurement for pressure?
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dynes per cm squared
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power = ?
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pressure squared
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what is the equation for SPL?
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20 log Px/Pr
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what is the equation for IL?
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10 log Ix/Ir
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what is the reference for sound pressure level?
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.0002 dynes/cm^2 or 2x10^-4 (two times ten to the negative forth)
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a dB is ______ times the log of an intensity ratio and _________ times the log of a pressure ratio
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10, 20
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why does sound fade away over time?
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due to frictional resistance and damping of vibration
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sound fades away over _______, over ________, and as it __________
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sound fades away over time, over distance and as it encounters obstacles
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compressions form a spherical shell, which is called a __________
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wave front
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at some distance from the source the spherical wave front becomes a _________
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plane wave front
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intensity varies ________ with the square of the distance
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inversely
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the inverse square law applies where?
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in a free and unbound medium
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if distance is doubled, sound intensity is decreased by a factor of _____, sound pressure is decreased by a factor of _____, and we lose ____ dB
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4, 2, 6 dB
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intensity it equal to ______?
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pressure squared
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what four things can happen when sound encounters obstacles?
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it can be reflected, refracted, diffracted, or absorbed
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when an obstacle has high impedence, this means it has _________ absorption
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low absorption
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reflection
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sound wave reflected back towards source with no change in the speed of propagation
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what happens to the inverse square law when we have obstacles?
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it does not hold
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with regard to wave reflection, the angles of the reflected rays will be what?
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perpendicular but equal to the angles of the incident rays
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what is another name for reflected waves?
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echoes or reverberating waves
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what is the opposite of a reverberent room?
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an anechoic chamber
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anechoic chambers minimize what?
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reflections
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reverberation time
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time required for sound energy to decay by 60 dB relative to its original level
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constructive interference
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- has reinforcing effects
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destructive interference
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- has canceling effects
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standing wave
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occurs when two progressive waves, incident and reflected, of same frequency and amplitude, travel in opposite directions in or along the same medium
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standing waves can either _____ or __________
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reinforce one another (constructive interference) or cancel eachother out (destructive interference)
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with standing waves, each wave is traveling but the resultant wave is _________
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stationary
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nodes
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locations of zero displacement in a standing wave
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antinodes
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locations of maximum displacement in a standing wave
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refraction
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the medium changes and sound bends as a result
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diffration
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the wave bends around an obstacle and reforms
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absorption coefficient
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proportion of energy in incident wave absorbed by material
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how is absorption related to reflection?
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they are inversely related
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any base raised to the power of 0 equals _____
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1
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any base raised to the 1st power equals _____
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the base, X^1=X
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the log of 1=
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0
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when you divide logarithms you _______ exponents
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subtract
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when you multiply logarithms you _____ exponents
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add
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measure of central tendency
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how much sound intensity is required for the average person to just barely detect it
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how do we plot the thresholds of audibility?
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as the threshold in decibels SPL as a function of frequency
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high sensitivity = _______ threshold
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low
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what frequencies does the ear transmit well?
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middle frequencies. It doesnt transmit low frequencies well dt stiffmness of eardrum and other structures and it doesnt transmit high frequencies well dt weight of ossicles/other stuctures
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what is the resonant frequency of the middle ear?
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approximately 1800 Hz
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minimum audible field threshold (MAF)
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SPLs for pure tones at absolute threshold measured in a free field. Listener in a room listening out of loud speakers with both ears 1 meter from the sound source
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minimum audible pressure (MAP)
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describe thresholds in terms of the sound pressure at/near the listeners tympanic membrane. It is dependent on the type of earphones used for testing
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when does pain sensation occur (dB wise)?
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120 dB and higher
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the auditory system requires _______ for maximal performance (time)
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300 msec
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time intensity trade off
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once you decrease the time, you must increase the power for the same level of performance (aka temporal integration)
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differential sensitivity
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how far apart two frequencies need to be in order for you to just tell a difference
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intensity discrimination
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the auditory system can detect about a .5 to 1.0 dB difference in intensities betwen two sounds across a broad range of frequencies/intensity levels
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a 50 msec tone would sound softer than a 60 msec tone due to ____________
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the time-intensity trade-off
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what are the three dimensions in which sound is localized?
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horizontal (left/right), vertical (up/down), range (near/far)
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does sound have spatial dimensions?
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no, sound in itself does not have spatial dimensions. We localize by using cues such as time of arrival of sound at the ear, intensity level at the ear, and frequency cues
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interaural time difference (ITD)
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the difference in time of arrival at each ear
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what sounds are able to more easily travel around corners?
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lower frequencies are more able to bend around corners, high frequencies can't
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what will happen with high frequencies trying to get aroudn the head from one ear to the other?
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they will lose intensity
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what sounds are easiest to localize?
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high and low frequency sounds. Mid-frequency sounds are harder.
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duplex theory of localization
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says there is 2 cues for determining where sound is coming from
1. which ear receives sound first 2. which ear receives louder singal |
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interaural time difference
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which ear receives the sound first
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interaural intensity difference
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which ear receives the louder signal
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what do we have to do when sounds come from directly in front of us?
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make small adjustments in head position as one ear does not receive the sound louder/first
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localization in the _______ plane is poorer than the _______ plane
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vertical plane is poorer than the horizontal plane
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minimal audible angle
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smallest distance you can detect between two sounds
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having a unilateral hearing loss effects what?
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localization and the ability to listen in background noise
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precedence effect
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echo suppression. When a sound from one direction is heard quickly followed by another sound, the perceieved sound is dominated by the earlier arriving
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what are the benefits of the precedence effect?
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suppresses the effects of reflections that might interfere with perception of the direct sound
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localization
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perception associated with an external sound source
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lateralization
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perception associated with headphones
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the cocktail party effect
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refers to the ability to discriminate sounds in background noise based on their spatial separation. This is why people can listen to speech when there is a lot of speech in the background noise
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kids with unilateral hearing loss in public schools....
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- repeat more grades than kids with normal hearing
- are described as more behaviorally problematic by teachers - do poorly on standardized tests |
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fused image
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what lateralization is sometimes referred to because the listener reports hearing one sound even though it is presented in both ears (with headphones)
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How often do sounds occur in isolation?
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rarely
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Why cant be test hearing lower than 20 dB in schools?
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because the background noise masks out soft tones used to test for hearing
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tonal masking
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how much does one tone mask another tone present at the same time?
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the masker can shift the ___________
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threshold
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an effective masker will change the _____________
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threshold
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T or F: sometimes a masker will not change threshold no matter how loud you make the masker
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T
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What maskers are most effective at masking the signal tone?
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those that are near the frequency of the signal tone
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Do maskers mask higher or lower frequencies better?
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higher
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_________ frequencies mask out high frequencies
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low
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what is true with regard to high frequencies and masking?
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high frequencies don't mask sounds very well
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over a wide range, the signam must be ___ to ____ dB above the white noise to be detected
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5 to 15 dB
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signal to noise ratio
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comparison of signal level to background noise. Subtract background noise from signal to get it.
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critical band
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frequencies near the signal tone that are critical for masking
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When noise is broader than the internal filter, _________ occurs
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maximum masking
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With narrow band noise is the signal esier or hearder to detect?
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easier, we are eliminating frequencies that contribute to masking
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at higher frequencies what do we need to mask tonal signals?
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a greater bandwidth (in hertz)
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T or False- we need more bandwidth to mask louder signals?
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T
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width of critical band for masking is proportional to its ___________
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center frequency
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