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Brittaney's Acoustics
Hearing Science- Acoustics
73
Audiology
Undergraduate 3
10/03/2010

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Term
Communication Systems
Definition
3 elements to a communication system:
sound source--signal--receiver
ex: larynx--speech--auditory system
Term
Components of a Sound Wave-- Wave motion must be either:
Definition
wave motion must either be transverse or longitudinal.
Term
What wave motion results in an air medium?
Definition
Longitudinal
Term
Wave motions produce what?
Definition
Compression and Rarefaction
Term
Simple Harmonic Motion
Definition
repetitive movement, back and forth (sine wave)
Term
Types of mediums and Velocities
Definition
air: 1,100 feet per second
steel: 15,000 feet per second
h2o: 5,000 feet per second
Term
Wavelength Formula
Definition
wavelength=velocity/frequency
Term
Standing Wave
Definition
A phenomenon in which sound reflects or bounces off of a hard surface, and there is no change in phase.
Term
If sound is in the same phase when reflected it:
Definition
cancels out
Term
If sound is not in same phase when reflected it:
Definition
creates an echo
Term
Measurable Characteristics of Vibratory Motion
Definition
displacement, amplitude, frequency, period, and phase.
Term
Displacement
Definition
at any instant, this is the distance from equilibrium to the position of the body at that point in time.
Term
Amplitude
Definition
the maximum displacement of a body from its position of equilibrium
Term
Frequency
Definition
number of complete vibration cycles (cps) per unit of time, usually in seconds- Herz
Term
Period
Definition
T (time) elapsed during a single complete vibration (frequency and period are inversely proportional)
Term
Phase
Definition
the portion of a cycle through which a vibrating body has passed at a given instant (expressed in degrees)
Term
Types of Vibration
Definition
Free
Forced
Maintained
Term
Free Vibration
Definition
continues to vibrate until all energy is dissipated (pendulum, tuning fork, vibrating spring)
Term
Forced Vibration
Definition
energy imparted on an object continues (stays in motion)
(ex- tuning fork against object)
Term
Maintained Vibration
Definition
constant supply of energy continuing to drive it
Term
Maintained Vibration
Definition
constant supply of energy continuing to drive it
Term
Damping
Definition
sound slows, and is eventually gone.
decrease in amplitude over time, due to an outside force
Term
Critical damping
Definition
vibrates and returns to equilibrium w/out passing through it (vibration is suddenly stopped, due to an outside force)
Term
Inverse Square Law
Definition
in any vibration- the intensity of a sound decreases proportionately to the square of the distance from the sound source: I=1/d^2 (where I=intensity, and D=distance)
Term
Complex Sound
Definition
produced by structures that vibrate in a complex manner: has harmonies and overtones, fundamental frequencies. Does not follow sinosoidal manner.
Term
Each mode of vibration of a complex sound...
Definition
...contributes to the overall shape of the resulting wave.
Term
Simple Sound
Definition
single solitary sound- sound wave pattern
Term
Steady State Sound
Definition
occurs when the frequency composition, amplitude, and phase of a tone are constant over time time. (ex: sustained vowel) No steady state sounds in speech!
Term
Sine Wave
Definition
Single solitary sound, repetitive movement back and forth
Term
Frequency Composition
Definition
all frequencies within a complex sound
Term
Periodic
Definition
a sound that repeats compressions and rarefactions at the same rate over a period of time
Term
Aperiodic
Definition
not repeatable, not steady or regular
Term
Fourier Analysis
Definition
process that breaks down the spectrogram of a complex sound (way to analyze a complex sound)
Term
Missing Fundamental
Definition
ear can hear fundamental even when missing (generalize)
Term
Overtones
Definition
any frequency within a complex sound that is higher than the fundamental frequencies
Term
Harmonics
Definition
integral multiples of a fundamental frequency
Term
Fundamental Frequency
Definition
lowest component of a complex sound
Term
What is the average fundamental frequency for men? Women?
Definition
Men= 125Hz
Women= 250 Hz
Term
Noise
Definition
-not composed of sound waves
-complex sounds not made up of harmonics
-can be "intermittent"
Term
What are the types of noise?
Definition
White Noise
Narrowband noise
Speech Noise
Term
White Noise
Definition
made up of a lot of puretones
Term
Narrow Band Noise
Definition
intensity centered on one particular band of frequencies
Term
Speech Noise
Definition
has most of its intensities centered around speech range (500Hz - 2000Hz)
Term
Masking
Definition
noise interferes w/our ability to hear speech
Term
Resonance
Definition
vibratory response to an applied force
Term
Which type of noise has the greatest masking effectiveness?
Definition
White noise
Term
Frequency
Definition
number of completed cycles per second (CPS)
Term
Intensity
Definition
-essentially how loud a sound is
-rate of energy flow per unit of area (per unit of time)
Term
As sound moves away from the sound source...
Definition
...the intensity decreases
Term
Intensity is expressed in....
Definition
...power and pressure
Term
Pressure
Definition
.0002 dynes/cm^2
Term
Power
Definition
10^-16 watts/cm2
Term
Log
Definition
the power to which the base must be raised to equal that number
Term
Decibels
Definition
based on a logrhythmic scale, measures relative intensity
Term
Bel
Definition
made up of ten decibels
Term
Phons
Definition
unit of loudness (dB) to equal that of 100Hz (only measured in a sound field)
A unit of perceived loudness that compares the loudness of a 100Hz tone to other frequencies. Loudness growth is greater in the low and high frequencies than the mid frequencies.
Term
Phon Curve
Definition
graphical representation of phons compared to decibels across the frequency range of about 20-10000Hz
Term
Phon curve is also known as the....
Definition
Equal Loudness Contour
Term
Threshold
Definition
softest level you can hear a sound
varies by person
Term
Minimal Audible Field
Definition
sound pressure level of a tone a threshold of audibility that is presented by a sound field
Term
Minimal Audible Pressure
Definition
sound pressure level of a tone at a threshold of audibility that is presented by an earphone.
Term
What is the difference between MAF & MAP?
Definition
when measuring MAF you are measuring intensity or SPL from where it hits the outer ear. The MAP measures SPL as it hits the eardrum.
Term
Just Noticeable Difference/Difference Limen
Definition
smallest difference in a stimulus value that a listener can detect
Term
^Intensity...
Definition
as things get louder, less of a dB change needed to notice a difference
Term
\/ Frequency
Definition
less intensity needed to notice a difference
Term
Signal Detection
Definition
trials are presented- half of which contain a stimulus, half of which do not
listener will respond either "yes" or "no"
Term
Signal Detection: Stimulus presented w/"yes" response
Definition
"hit"
Term
Signal Detection: Stimulus presented w/"no" response
Definition
"miss"
Term
Signal Detection: Stimulus not presented w/"yes" response
Definition
"false positive"
Term
Signal Detection: Stimulus not presented w/"no" response
Definition
"correct rejection"
Term
Spectrum Level
Definition
intensity of any one frequency in a band of noise
Term
Bandwidth = ?
Definition
highest frequency minus the lowest frequency
Term
2 sounds of equal sound pressure level in an unequal bandwidth....
Definition
sound w/narrower bandwidth has higher spectrum level
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