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93 Cards in this Set
- Front
- Back
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what is the physical definition of sound
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series of vibrations of molecules in a medium
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what can constitute a medium
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gas, liguid, solid
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sounds are waves of tine flucuation in ____ ________ that ________ ( ) from the source
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air pressure, propagate (radiate)
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our ear drums ______ when those presssure waves reach our ears
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vibrate
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the auditory system converts the pressure waves to _____ ______ that the brain processes, interprets and classifies
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neural impulses
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air occupies space and there is a relationship between volume and ________. which is known as what law
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air pressure...boyles law
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a vibrating tuning fork causes localized _____ _____ changes by displacement of molecules next to the tines which push against their neighbors and so on. setting up a wave of energy of small increases and decreases in ambient pressure that propagates through space
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air pressure
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the cycle of increased pressure is
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compression phase
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the cycle of decreased pressure is
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rarefaction phase
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how does sound occur
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an object is vibrated by a force.
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what two things does an object need in order to vibrate
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elasticity and inertia.
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what is inertia
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force must be acted on by an object to make it move
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what is elasticity
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ability of an object to return to initial position after movment.
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how does a pendulum illustrate the need for inertia and elasticity
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without elasticity the pedulum would just continue out to one side into infinity. without inertia, the pendulum would not continue once straight up and down.
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what is the point of dispacement
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when it swings out to first sidee
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what is max displacement
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as far as it will go
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what is positive max displacement
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first side it swings to
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what is neg max displacement
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second side it swings to
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how many frequencies are there in a sine wave...what type of tone is a sine wave
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pure tone. 1 frequency
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what does a sine wave have the same trajectory as
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a circle
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what is the degree at the point of rest
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0
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if a tree falls in teh forst and there is noone there to hear it does it make a sound? what are the two sides of the answer
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1. depends if you think sound needs an ear to receive it
2. you can say the molecules moved so there is sound |
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do we often hear sine waves in our lives
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no, most sounds in our lives are complex
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what is vibratory motion
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movement that occurs when as object is set into motion by a force
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what is the simplest pattern of vib. motion called
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sinusoidal or sine wave
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describe the displacement of the vib. object with a sine wave
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continuous, regular, back and forth displacement
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when does displacement occur
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when an object is acted on by a force
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what is the displacement pattern of a sine wave called
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simple harmonic motion
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in sine wave, displacement around rest is _______
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symmetric
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the vibrating pattern of a given sine wave repeats itself into -______
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infinity
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what constitues a cycle for a sine wave
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1 transition of motion. from 0-360 degrees
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what are the five ways to describe simple harmonic motion
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1. frequency
2. period 3. amplitude 4. phase 5. wave length |
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what is the definition of frequency? what is the units? what is the psychological corelate
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# of cycles completed in a second. hertz (Hz). pitch
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describe the relationship between pitch and frequency. and the reason
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they are related but are not a 1 to 1 relationship. reason: frequency is measured but pitch is just in your head- no way to measure
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what is the definition of period? what is it measured in?
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amount of time it takes to complete 1 cycle. units time (T). usually measured in seconds or milliseconds
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definition of amplitude.
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strength of vibration of molecules. amount of vibratory displacemnt; distance molecules are displaced from object @ rest
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psychological correlate
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loudness
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4 ways to measure amplitude
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1. instantaneous amplitude
2. peak amplitude 3. peak to peak amplitude 4. rms amplitude |
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instantaneous amplitude varies with
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time
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what is inst. ampl
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measure of amplitude at any point in time across the wave. time dependent
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peak amplitude
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amount of amplitude at points of max displacement
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peak to peak amplitude
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from 1 point of max displacement to another. add the two together. take absolute valeu of neg. max. displ.
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rms amplitude
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root mean square. average. purpose: want the average instantaneous amplitude of a sine wave. take the amplitude values and square them. then get the average of squared numbers. then take square root.
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what is the easy way to find rms
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peak amplitued x 0.707
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what kind of waves are used in hearing tests
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sine waves
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in hearing tests, what is the purpose of rms?
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rms ampl. is used to compare sine waves and says which one is louder.
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phase
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point in the cycle where the object begins to vibratef
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what is phase measured in
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degrees.
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instantaneous phase
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the measurement of phase at any point along the wave.
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wavelength
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the distance between two consequtive positive peaks or two consequtive negative peaks on a sine wave.
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what are the two things that wavelength is effected by
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frequency and speed of sound in air
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what is the constant (speed of sound in air)
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344 meteres/second
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does wavelength increase or decrease as frequency increases and why
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increases. frequency = cycles per second. will be much closer together as frequency increases. shorter wave lenght
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what is intensity a measure of
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of sound strength
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what is the purpose of log rhthms
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condences log #'s. scientific short hand.
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intensity = (one word)
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loudness
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unit for intensity
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decibels (dB)
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is decibel a ratio or an absolute value
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ratio
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ratio is what
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comparison
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decibel is (one word)
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pressure
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4 types of decibel
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1. dBSPL- sound pressure level
2. dBIL - intensity level 3. dBSL- sensation level 4. dBHL- hearing level "clinical decibel" |
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dBSPL- two things u need
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1. measured pressure- will be given
2. reference pressure- will be memorized |
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Pr=
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reference pressure
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what are the two reference pressures and how do you know which to use
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1. Pr= 20 mPa
2. Pr= 2 x 10^-5 0.0002 Pa pick which to used depending on the unit of hte measured pressure. |
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does 0 dBSPL mean no sound
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no. dBSPL is a ratio. measured pressure/reference pressure. means the reference pressure and measured pressure are the same thing. there is very soft sound at 0 dBSPL.
100 dBSPL is not 100x louder than 0 dBSPL. |
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how many dBSPL for a jet engine? for leaves on a tree?
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120, 15
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what is dBSL
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decibel sensation level.
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what is a sensation
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a sound in comparison to another. since they are being compared must have like values.
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what is the dBSL for 30 dBSPL and 75 dBSPL
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45 dBSL. tone 2 is 45 dBSL compared to tone 1.
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what is dBHL
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clinical decibel. antime a hearing test is given- it is dBHL. hearing level is always talked about in dBHL
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what is a complex wave
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any wave that is not a sine wave but is composed of a series of sine waves that can differ in amplitude, frequency and phase
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2 types of complex waves
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1. complex periodic wave
2. complex aperiodic wave |
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what does complex mean about frequency
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more than one frequency
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periodic means what
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it repeats itself
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complex periodic wave.
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several sinusoids summed- not randomly chosen.
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wave has ________ pattern
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predictable
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added sines are ____________ related
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harmonically
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they are ______ _______ nultiples of one another
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whole number
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150->
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300-> 450-> 600
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series starts with the sine of the _______ frequency called the________ aka________
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lowest. fundamental frequency. first harmonic
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complex aperiodic wave
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no relationship between sine waves. no repeatable pattern.
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example of sound with aperiodic wave? what is the behavior of hte instantaneous amplitude
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noise. instantaneous amplitude varies over time in a random manner. no dicernible pitch.
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examples of aperiodic wave
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sounds like steam hissing. /s/, /f/, /h/. snow on a tv.
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resonant freqency
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when a vibrating object is set into free vibration, it will vibrate at a frequency determined by its physical properties including mass, elasticity, and tension
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the natural frequency of a ________, ________, __________ are examples of resonance
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tuning fork, pendulum, ear canal
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what is the resonant frequency when something is under forced vibration
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you're doing something to it. a drum when u hit it. the resonance frequency is that at which the least amount of energy imput is required.
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can an enclosed volume of air resonate why why not?
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yes. because air is anelastic medium, it can be alternately compressed and expanded
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filters
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special examples of resonators that remove some frequencies while allowing others to remain. cut off frequency.
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4 kinds of filters
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1. high pass
2. low pass 3. band pass 4. band reject |
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high pass filter
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removes frequencies below the cut off. passes the high
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low pass filter
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removes frequnecies above the cut off. passes the lows
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band pass filter
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has 2 cut off frequencies. everything between teh two cut off gets passed.
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band reject
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2 cut off frequencies. what is inside gets filtered
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