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| refers to the maximum displacement of the particles of a medium,it is related perceptually to the magnitudeof the sound volume and loudness |
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| indicates the energy(intensity)of a sound it is usually measuredfrom the baseline(point of rest )to the point of maximum displacementon the wave form. |
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| the linear measurement is called,the distance between the baseline and the point of maximum displacement is related to the movement of the swinging pendulum or tuning fork tine as it moves from rest to maximum excursion in one direction |
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| amplitude is related to the point of maximum vibration of a particular vibrating objects. |
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| it represents maximum excursion of the mass from its rest position |
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| in the case of the human vocal folds |
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| the amplitude of the sound being produced is related to the maximum excursion of the vocal folds away from the midline during each cycle of vibration. |
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| are spread apart during each cycle the greater is the resulting amplitude of the sound being produced. |
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| in some instances amplitude |
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| measurements are made on the sine wave tracings from the maximum displacement in one direction to the point of maximum displacement in the other direction instead of from baseline to the point of maximum displacement in one direction. |
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| in both instances would be the same but the method of measurement would be different leading to different linear readings . |
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| it is important to indicate whether the amplitude being reported is in terms of peak or peak to peak measurements. |
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| amplitude is related to the measurement |
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| of intensity which can be expressed in terms of sound pressure level or power. |
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| is the most common unit used to express sound intensity when amplitude is being expressed in terms of sound pressure or power it is a logarithmic unit used to express ratios between pressures or powers of sounds. |
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| is a linear measurement that refers to the distance a sound wave disturbance can travel during one complete cycle of vibration. |
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| can be defined as the distance between points of identical phase in two adjacent cycle of a wave .it can be expressed in feet or meters it is inversely related to the frequency or the sound being produced. |
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| is a time concept referring to vibrator movement from rest position to maximum displacement in one direction to rest to maximum displacement in the opposite direction and back to rest again. |
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| is the time (usually expressed in seconds)that it takes for a vibrator to complete one entire cycle of vibration. |
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| is the number of complete cycles that occur during a certain time period usually one second. |
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| in cycles per second (cps)or hertz in honor of heinrich hertz the first person to demonstrate electromagnetic waves. |
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| or tuning fork tine or mass in the spring mass model completes 100 cycles in one second its frequency of vibration is 100 cps or hz. |
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| of a signal is the perceptual correlate of frequency. |
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| pure tone would be perceived as being lower in pitch than a 1,000hz pure tone |
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| pitch determination requires human perceptual judgements of the sound |
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| in this case of human v.folds |
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| vibrations frequency is determined by the number of openings and closings of the vocal folds that occur in one second. |
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| if the folds open and close 100 times |
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| in a single second the frequency of their vibration is 100 (cps)or (HZ) |
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| there is an inverse relationship between period |
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| and frequency since period is the time needed for the completion of one cycle of vibration as frequency is increased(more cycles per second) |
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| period will be reduced (less time for the |
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| completion of any one particular cycle. |
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| thus as frequency is increased |
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| period is decreased proportionately |
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| hz will have a longer period1/250 or 0.004 seconds than one of 1,000hz 1/1,000 or 0.001 seconds. |
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| the reciprocal relationship between period and |
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| frequency is expressed in the following formula frequency=1/period |
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| if the frequency of vibration |
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| for a particular sound wave is 1,000hz the period would be 0.001 second=1/1,000hz=0.001 second |
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| exists between the time concept of frequency and the spatial concept of wavelength. |
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| as frequency is increased |
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| wavelength becomes shorter and as frequency is increased wavelength becomes shorter. |
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| as frequency is decreased |
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| since the number of cycles |
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| are increased within the same unit of time (a second)each cycle will take less time and cover a shorter distance. |
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| it is an established fact |
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| in environmental acoustics that lower frequencies are more difficult to absorb than higher frequencies because of the longer wavelengths of power frequencies. |
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| a frequency of 100 hz for example |
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| has a wavelength of 11 feet while a frequency of 10,000 hz has a wavelength of only 0.11 feet. |
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| the 10,000 hz tone could be asborbed |
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| by acoustical ceiling tile that is only a few inches thick. |
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| however the 100 hz frequency |
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| would require an unusually thick wall or some other type of acoustical treatment for it to be completely absorbed. |
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| the relationship between frequency |
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and wavelength can be expressed in the following formulas.=velocity/frequency
v/sideward t |
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| where f is frequency sideward t is wavelength |
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| v is velocity a constant refers to the speed of sound |
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| if the frequency of vibration for a particular sound wave |
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| disturbances is 100 hz the wavelength for that frequency is 11.0 ft or 3.4 meters wavelength =velocity /frequency;1,100ft per second /100 hz=11.0feet 340 meters per second/100hz=3.4 meters;34,000 centimeters per second /100 hz=340 centimeters |
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| if the unit of measurement for velocity |
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| is feet per second then the wavelength is expressed in feet. if the unit of measurement is meters per second then the wavelength is expressed in meters.it is important to note that the answer is not expressed in feet or meters per second but in feet or meters. |
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| is a linear measurement of the distance covered by a sound wave disturbance during one cycle of its vibration. |
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| for a particular sound wave disturbance is 1.1 feet or 0.34 meters the frequency for that sound wave disturbance would be 1,000hz frequency = velocity/wavelength :1,100 feet per second /1.1 feet=1,000hz:340 meters per second/0.34meters=1,000hz |
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| is the speed of sound through a transmitting medium the average speed of sound in the medium of air is approximately 1,100 feet per second or 340 meters per second or 34,000 centimeters per second |
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| there are some differences |
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| in the speed of sound in air as velocity is measured at different heights above sea level |
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| in air is relatively constant because of the elastic and inertial properties of a given medium |
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| water has different elastic |
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| and inertial properties than does air and consequently the speed of sound is faster in water than in air. |
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| the velocity of sound varies as a function of the elasticity density and temperature of the transmitting medium with elasticity being the most important factor |
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| the greater the elasticity |
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| (springness) of a medium the greater the velocity the greater the density of the medium mass per unit of volume the slower the velocity. |
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| in medium A than i medium B |
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| and therefore the potential speed of movement of cars on a highway(medium) A is greater than on highway (medium)B |
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| temperature has an indirect |
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| effect on velocity: an increase in temperature causes a decrease in density in a medium which in turn causes an increase in velocity. as proof consider the situation if a solid is placed in an oven as the tempertature increases the solid will turn to a liquid and eventually to a gas in progressing from a solid to a liquid and then to a gas via an increase in tempertature density has decreased as well. |
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| sound waves are lw the particles of a medium move in the same line of propagation as the wave that is in the same direction as parallel to the movement of the wave . |
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| the particles of the medium move perpendicular at right angles to the movement of the wave.(for example) while the wave may be moving from right to left the particles are being displaced up and down from their rest positions . |
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| are transverse waves a fact that becomes apparent when a rock is thrown into a pond and ripples waves in the water result. |
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| while the waves are moving out in a |
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| concentric circular manner from the disturbance producing rock the water particles are moving up and down ,perpendicular to the wave motion. |
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| while transverse waves(sine curves) |
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| are used to illustrate the various properties of sound waves,amplitude,wavelength,period ,cycle in reality sound waves are more easily illustrated on transverse waves. |
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| that is set up in an appropriate medium is spherically propagated through the medium. |
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| outward in all directions from the sound source until it strikes an object that would alter its spherical pattern. |
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| verifies the fact that sound propagation is spherical in natureby showing the predictabilityof amplitude measurements at specified distances from the sound source. |
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| that there is an orderly relationship between a decrease in sound amplitude and the distance that it is measured from the sound source. |
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| of a sound at a given distance from the sound source is inversely proportional to the square of the distance of the point of measurement from the sound source. |
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| a sound of a given intensity has one ninth 1/(3)2) of its orginal intensity at three times the distance from a sound source. |
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| required for the inverse square law is that the soundwave being measured does not strike an object prior to the amplitude measurement. |
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| is of little practical value bc the world we live in has sound barriers and a sound disturbance usually does not emanate too far from its originating source before it strikes an object of some kind. |
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| once a sound wave strikes an object |
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| several things can happen to it. |
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| the sound energy being emitted |
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| can be (ABSORBED)by the object that has been struck |
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| if the object is a wall with absorptive |
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| properties the sound energy enters the structure is converted to thermal energy heat and then is dissipated. |
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| strikes an object it can bounce off the object. |
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| bounces of a wall it is said to be (REFLECTED) |
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| are multiple or continuous to the point that they actually prolong the existence of the sound within a confined space they are referred to as (REVERBERATIONS) |
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| The prolongation of a sound |
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| through multiple or continous reflections. |
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| interference in the transmission of sound waves is (REFRACTION) or (Deflection) |
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| which is the bending of sound waves from their path of propagation as a result it changes in the determinants of velocity in the medium. |
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| tend to move outward from the sound source in the form of a spherical wave,after approprimately six feet out from the sound source, |
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| a plane flat surface and thus the wave is a (plane wave) |
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| varies in different locations in the medium thereby causing variations in the velocity of sound waves in that medium then the wavefront might be tiltedthereby changing the direction of the propagation of the wave-soundrayand causing a bending(refraction) of the way from its original path of propagation which can cause a distortion of the sounds being transmitted. |
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| effects can be seen in rooms with very tall ceilings in which the temperature varies at different room locations warmer on the ceiling than on the floor |
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| in the intelligibility of sounds at different locations in these rooms. |
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| an amplitude by time display of sound. |
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| harmonic motion the waveform graph clearly displays amplitude changes as a function of time. |
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| another method for displacing |
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| sound is to graph it in terms of amplitude as a function of frequency. |
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| is plotted as a function of frequency the resulting graph is referred to as a spectrum. |
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| a graphic representation of the frequency and relative amplitude of the components of complex sounds. |
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| a spectrum for simple sounds |
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| (pure tones) would consist of a single line located at the appropriate frequency. |
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| of the single line would be equal to the amplitude of the( pure -tone )that has been graphed. |
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| shows amplitude as a function of frequency at a single instant in time and has the advantage of allowing frequency to be read directly from the display. |
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| advantage of showing amplitude changes over time but frequency has to be calculated . |
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| provides little advantage when viewing simple sound disturbances because all of the energy is concentrated at a single frequency. |
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| complex sounds in which there is energy at more than one frequency the sound spectrum becomes more valuable. |
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| differ from simple sounds in that they have energy distrubited at more than one frequency. |
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| generates a sound with energy concentrated at one frequency . |
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| of different frequencies are activated simultaneously,the sound generated will consist of two frequencies and will therefore be considered complex in nature. |
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| will no longer show curves like that of sine wave and the spectrum will have two vertical lines,each line representingthe frequency of vibration of one of the tuning forks vibrating simultaneously with the other. |
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| like those for vowels are very complex in that they have energy distruibited at numerous frequencies,with amplitude variations at each of the frequencies involved. |
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| a periodic sound disturbance |
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| is one in which the wave shape repeats itself as a function of time;that is the wave shape is said to have (periodicity) |
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| when the wave shape of a sound repeats itself over time the sound heard is usually tonal in nature. |
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| provides simple harmonic motion is by definition ,periodic |
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| a pendulum or tuning fork tine. |
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| the puretone has a clearly defined |
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| frequency because of the cyclical(periodic)behavior of the vibrator generating it. |
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| while the vowels of english |
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| are not simple sounds like the pure tone ,they are periodic because of the cyclical nature of the sound generator. |
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| employed during their production. |
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| open and close in a rythmic manner during the production of vowels causing repetitive (technically quasiperiodic) wave shapes to occur. |
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| a french mathematician who lived in the early part of the nineteenth century,showed that any complex periodic sound wave disturbance can be mathematically broken down into its individual sine wave(puretone) components which vary in terms of frequency,amplitude and or phase with respect to one another . |
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| analysis of complex signals into their sinusoidal components called (Fourier analysis) |
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| a mathemical system for analyzing complex periodic soundsinto the individual pure tones of varying frequency,intensity,and phase of which they are composed. |
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| is the portion of a cycle through which a vibrator has passed up to a given instant in time; it is concerned with the timing relationship between individual sinusoids. |
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| two sinusoids are in phase |
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| when their wave disturbances crest and trough at the same time. |
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| does not seem to detect phase differences or to use them to any great degree in the interpretation of the speech signal |
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| if frequency,amplitude,and phase are all considered together |
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| fourier analysis can be used to determine the sine waves that are combined to produce any complex periodic sound disturbance. |
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| an aperiodic sound disturbance |
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| is one in which the wave shape does not repeat itself as a function of time and is therefore said to have (APERIODICITY) |
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