# Shared Flashcard Set

## Details

COMD 451
Chapters 3-6 Vocab
118
Audiology
02/22/2010

Term
 Period
Definition
 The time required for the completion of one cycle of a periodic motion.
Term
 Frequency
Definition
 The number of cycles per second.
Term
 Oscillation
Definition
 Any back and forth movement between two states.
Term
 Vibration
Definition
 Mechanical oscillation with elasticity acting as the restoring force.
Term
 Sinusoidal motion
Definition
 The motion of an object in which changes in displacement, velocity, and acceleration are sinusoidal functions of time.
Term
 Periodic motion.
Definition
 A motion that repeats itself in regular intervals until stopped by an external force.
Term
 Harmonic motion
Definition
 A motion in thich the acceleration of the object is directly proportional but opposite in direction to the displacement of the object from its equilibrium position.
Term
 Waveform
Definition
 A function representing changes of any physical quantity as a function of time.
Term
 Propagation
Definition
 Process of conveying energy through space via a wave motion.
Term
 Mechanic wave
Definition
 Transfer of mechanic energy from one molecule to another.
Term
 Medium
Definition
 A substance that occupies a space; can be solid, fluid, or gas.
Term
 Mechanic disturbance.
Definition
 Any event that causes a change in medium at a specific location.
Term
 Longitudinal waves
Definition
 Waves in which the particles of the medium are displaced in the same direction as the wave propagation.
Term
 Compression
Definition
 Bunching of particles causing increased density.
Term
 Rarefaction
Definition
 Spreading of particles causing decreased density.
Term
 Transverse waves
Definition
 Particles of a medium are displaced in a directon that is perpendicular to the direction of wave propagation.
Term
 Surface waves
Definition
 Complex waves created when a mechanic disturbance arrives at a border between two media having different densities; combination of transverse and longitudinal waves.
Term
 Sound
Definition
 A disturbance in an elastic medium that propogated through the medium as a longitudinal wave; a stimulus that causes an auditory sensation.
Term
 Speed of sound
Definition
 The rate at which energy propagates through a medium.
Term
 Wavelength
Definition
 The distance in space between two adjacent identical points of a propagating wave.
Term
 Sound energy
Definition
 The energy transferred from the vibrating source to the medium and propagates through the medium in the form of density changes.
Term
 Infrasound
Definition
 Very low frequency sounds that cannot be heard (below 20Hz).
Term
 Ultrasound
Definition
 Very high frquency sounds that cannot be heard (above 20kHz).
Term
 Pure tone
Definition
 Tone with only one frequency.
Term
 Complex tone
Definition
 Tone with more than one frequency.
Term
 Deterministic sounds
Definition
 Sounds where maginitude at different points in time can be predicted.
Term
 Stochastic sounds
Definition
 Sounds where future behavior cannot be predicted; random.
Term
 Stationary noise
Definition
 Random sound with acoustic properties that do not vary much over time.
Term
 Nonstationary noise
Definition
 Noise content and intensity change randomly and noise properties cannot be predicted over time.
Term
 Phase difference
Definition
 The absolute difference between that phases of two waveforms with neither considered as a point of reference; maximum difference = 180 degrees.
Term
 Phase shift
Definition
 The relationship between the phase of one waveform and another where one is considered the point of reference.
Term
 In-phase
Definition
 When two waveforms have the same frequency and phase.
Term
 Out-of-phase
Definition
 When two waveforms have the same frequency, but different phases.
Term
 Instantaneous magnitude
Definition
 The magnitude of a waveform observed at any given time.
Term
 Amplitude
Definition
 The maximum/peak magnitude of a waveform.
Term
 Peak-to-peak magnitude
Definition
 The whole range of magnitude changes within one period.
Term
 Average magintude
Definition
 The average value of the magnitude calculated across the whole period of a waveform.
Term
 Root mean square (RMS) magnitude
Definition
 Constant magnitude derived from the root of the mean of the squares of the instantaneous magnitudes calculated across the waveform's period.
Term
 Stiffness
Definition
 A mechanical property of an elastic object that describes its opposition to the change of its dimensions by an external force.
Term
 Closed system
Definition
 A system that does not exchange its energy with the environment; no loss of energy.
Term
 Open system
Definition
 A system that loses part of its energy to the surrounding environment due to the effect of friction.
Term
 Free vibration
Definition
 The back and forth vibration of a system in which no additional energy is added once it is set into motion.
Term
 Resonant frequency
Definition
 The natural frequency at which a system will vibrate when left alone.
Term
 Forced vibration
Definition
 A vibration in which a system is forced to vibrate by an applied force.
Term
 Friction
Definition
 The force that opposes the relative motion of two bodies in contact and causes the conversion of system energy into heat.
Term
 Damping
Definition
 The loss of energy in a vibrating system due to dissipation to the surrounding environment; causes a gradual decrease in amplitude.
Term
 Minimally damped system
Definition
 Very little system friction.
Term
 Critically damped system
Definition
 Indicates the most rapid response to a sudden change of force without overshooting the equilibrium.
Term
 Heavily damped
Definition
 A lot of system friction.
Term
 Time constant
Definition
 Specifies time in seconds after which the amplitude of vibration decreases by ~63%.
Term
 Rise time
Definition
 The overall duration needed to change from 10% to 90% of a waveform's peak.
Term
Definition
 The time period during which a waveform has a relatively constant amplitude.
Term
 Fall time
Definition
 The time needed for a waveform to change from 90% to 10% of its peak value.
Term
 Resonance curve
Definition
 The dependence of the amplitude of vibrationof the frequency of the driving force.
Term
 Complex vibration
Definition
 The sum of two or more simple vibrations.
Term
 Fourier theorem
Definition
 Any complex waveform is the sum of various sinusoids of varying amplitude, frequency, and phase.
Term
 Aperiodic vibration
Definition
 A vibration without a repeating pattern.
Term
 Periodic vibration
Definition
 Vibratory motion in which an object returns to the same point in space at equal periods of time during the motion.
Term
 Waveform synthesis
Definition
 The process of combining several sine waves into a complex waveform.
Term
 Harmonics
Definition
 Whole-number multiple frequency components of a complex waveform.
Term
 Greatest common factor
Definition
 The largest common factor from a group of harmonically related components is equal to its fundamental.
Term
 Missing fundamental
Definition
 When the GCF of a set of harmonics is not present in the waveform.
Term
 Periodicity
Definition
 The concept that a periodic waveform repeats itself for an infinite amount of time.
Term
 Noise
Definition
 Random sequence of events resulting from the combination of a large number of unrelated frequencies.
Term
 Transient
Definition
 A brief, single event that ceases to exist after a very short time.
Term
 Complex inharmonic motion
Definition
 The sum of a finite number of frequencies that does not repeat its pattern within an observed period of time.
Term
 Waveform analysis
Definition
 The process of taking complex waveforms apart into individual components.
Term
 Time domain
Definition
 Representation of a phenomenon as a function of time.
Term
 Spectrum
Definition
 A graphical representation of a complex waveform showing the waveform energy (amplitude) of the individual components (y-axis) arranged in order of frequency (x-axis).
Term
 Frequency domain
Definition
 Representation of a phenomenon as a function of frequency.
Term
 Line spectrum
Definition
 A spectrum that consists of one or more separate vertical lines.
Term
 Amplitude/frequency spectrum
Definition
 Displays the amplitude of various vector quantities associated with the components (velocity, force, displacement, etc.).
Term
 Continuous spectrum
Definition
 A spectrum in which the energy of spread across a wide range of frequencies rather than at discrete sinusoidal components.
Term
 Power spectrum
Definition
 Displays the power (energy) of the components.
Term
 Nodes
Definition
 The points of the vibrating system at which displacement remains zero.
Term
 Antinodes
Definition
 The points at which the vibration magnitude is greatest.
Term
 Mode of vibration
Definition
 The specific vibration pattern of a vibrating system associated with each rosonance frequency of the system.
Term
 Impedance
Definition
 The opposition to the flow of energy through a system and any change in its state.
Term
 Resistance (R)
Definition
 The opposition of a system to movement caused by friction.
Term
 Reactance (X)
Definition
 The opposition of a system to a change in its state by the system's ability to store energy and prevent its transfer to or from another system.
Term
 Mass reactance
Definition
 The ability of the mass to store energy.
Term
 Stiffness reactance
Definition
 The ability of the stiffnes to store energy.
Term
 Conductance (G)
Definition
 The wase with which energy travels through a friction element in the system.
Term
 Susceptance (B)
Definition
 The ease with which energy travels through a stiffness element in the system.
Term
 Mass susceptance
Definition
 The ease with which energy flows through a mass.
Term
 Sitffness susceptance
Definition
 The ease with which energy travels through s spring element.
Term
Definition
 The ease with which a system can vibrate due to an applied force.
Term
 Impedance matching
Definition
 The practice of making the impedance of the source of power equal to the impedance of the load to transfer as much energy as possible from the source to the load.
Term
 Mass dominated
Definition
 If mass reactance is greater than stiffness reactance.
Term
 Stiffness dominated
Definition
 If stiffness reactance is greater than mass reactance.
Term
 Sound absorption
Definition
 Sound wave will lose energy due to absorption by the medium and surrounding boundaries.
Term
 Absorption coefficient
Definition
 The ability of a medium and its boundaries to absorb the energy of sound waves.
Term
 Sound reflection
Definition
 The bouncing of sound waves off of a boundary.
Term
 Sound refraction
Definition
 The bending of sound waves due to a change in the speed of sound propagation; caused by sound waves entering a different medium or changes in temperature.
Term
 Incident wave
Definition
 The original, incoming sound wave.
Term
 Total internal reflection
Definition
 A situation where 100% of the sound energy reaching a boundary is reflected back into the original medium.
Term
 Critical angle of incidence
Definition
 The smallest angle of incidence for which total internal reflection can occur.
Term
 Thermal effect
Definition
 The effect of bending sound waves away from the ground when warmer air is nearer to the ground and colder air is above it.
Term
 Inverse thermal effect
Definition
 When colder air is closer to the ground and warmer air is above it, waves bend toward the ground.
Term
 Reverberation time
Definition
 The time needed for a sound pressure to decrease 1000 times after the sound source ceases its operation.
Term
 Reverberation
Definition
 The reflected sound energy within an enclosed space.
Term
 Reverberation chamber
Definition
 Closed spaces with highly reflective surfaces that do not absorb sound waves.
Term
 Anechoic chambers
Definition
 Rooms with very soft walls, ceilings, etc. that absorb most of the sound energy.
Term
Definition
 An area behind a boundary that the direct sound waves does not enter.
Term
 Sound diffraction
Definition
 The phenomenon of sound waves bending around objects and through openings in barriers.
Term
 Constructive interference
Definition
 An increase in amplitude of sound waves when two or more sund waves travel through the same space and are in-phase.
Term
 Destructive interference
Definition
 A decrease in the amplitude of at least one sound wave when two sound waves travel through the same space and are out-of-phase.
Term
 Beats
Definition
 Slow, periodic amplitude fluctuations caused when two sine waves that are very close to each other in frequency interfere with one another.
Term
 Sound field
Definition
 A space containing sound waves.
Term
 Near field
Definition
 The resulting vibrations in a sound pressure near the sound source; characterized by large and nonuniform maxima and minima in acoustic pressure that gradually disappear into a uniform signal with increasing distance from the source.
Term
 Far field
Definition
 The region of uniformly decreasing sound pressure (1/r) observed far away from the sound source.
Term
 Direct sound field
Definition
 Sound field created by a sound source in an unbound space.
Term
 Free field
Definition
 Sound field in which sound propagation is not affected by objects or boundaries.
Term
 Indirect field
Definition
 Sound field where sound energy reflected from space boundaries dominates the sound energy propagating from the sound source.
Term
 Diffuse sound field
Definition
 And area filled with sound energy from random reflections coming from all directions and in which all SPLs are the same.
Term
 Critical distance
Definition
 The distance from the sound source where the intensity of both fields is about equal.
Term
 Signal-to-noise ratio
Definition
 The ratio of intensity of a signal to the intensity of a noise.
Term
 End correction
Definition
 Additional length added to a mass of a vibrating system to determine the resonance frequency of a tube with an open end.
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