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Intro to Aud. Ch 3

Sound and its measurement

TermDefinitionextra info
Sound A stimulus that has the capability to produce an audible sensation Sound may be defined as a psychological or physical phenomena
stimulus An oscillation or vibration in a medium
Components of sound There has to be an ENERGY SOURCE, an OBJECT capable of vibration, a MEDIUM, and a RECEPTOR (occurs in the psychological definition only)
Sound-Energy source produces the sound ex: you can't just hold a tuning fork, you have to apply energy or force to make it vibrate
Sound-object the object has to be capable of vibration ex: tuning fork, guitar string
sound-medium how we transmit the vibration to the ear air is a medium because the molecules are moving, the skull can be a medium because it moves when the fork touches it, water can also be a medium
vibration when an object is at a point of rest then moves from the point of disturbance striking and bouncing off adjacent molecules
Sound-receptor someone capable of hearing the sound
Simple harmonic motion The simplest pattern of vibration
pure tone a tone of only one frequency (no harmonics) seldom appear in nature, usually created by devices like tuning forks or electronic sine wave generators
sinusoid(al) or sine waves the waveform of a pure tone showing simple harmonic motion
waveform a vibrating pattern that presents a smooth wave made up of frequency and period
one cycle movement from equilibrium to maximum displacement in one direction, back to equilibrium, on to maximum displacement in the opposite direction and then back to equilibrium
oscillation the back and forth movement of a vibrating body
frequency the number of complete oscillations (cycles) of a vibrating body in a 1 sec period of time frequency is displayed in Hertz (Hz) or cycles per sec (cps)
Period amount of time it takes to complete 1 vibration of a cycle ex: if frequency is 3Hz the period (T) equals 1/3 sec
amplitude distance a vibrating object moves from its point of rest the louder the sound, the greater the amplitude
amplitude is correlated with loudness
frequency is correlated with pitch
cancellation reduction in amplitude to zero because of interaction of two tones 180 degrees out of phase the reduction of the amplitude of a sound wave to zero
complex sound energy at a number of different frequencies, amplitudes, and phase relationships composed of two or more pure tones comprised of periodic or aperiodic waves
Fourier analysis any complex wave can be decomposed to determine the amplitudes, frequencies and phases of the sinusoidal components sound waves can be classified by its reference to periodicity and complexity
periodic wave a waveform that repeats itself over time a musical note is always the same so it is a periodic sound
aperiodic waves a wave that lacks periodicity, no repetition, vibratory motion is random, usually perceived as noise the sound "sh" is random, not repeatable
fundamental frequency the lowest rate of a sound's vibration determined by the physical properties of the vibrating body
harmonics (overtones) any whole number multiple of the fundamental frequency of a complex wave each sinusoid in the series must be an integer multiple of the lowest in the series. ex: if lowest=100Hz, components are 100, 200, 300, 400, 500 etc
Phase the relationship in time between two or more waves
starting phase the angle in degrees at the moment rotation begins note: wave travels counter clockwise from 0°-360°
resonance the ability of a mass to vibrate at a particular frequency with least external force
watt a unit of power
exponent a logarithm
intensity the amount of energy per unit of area
velocity the speed of a sound wave in a given direction
wave a series of moving impulses set up by a vibration
dyne a unit of force just sufficient to accelerate a mass of 1 gram at 1 cm per second squared
fourier analysis that breaks a wave into its components
erg unit of work
cycle complete sequence of events of a sine wave through 360 degrees
decibel ratio between two sound pressures or two sound powers
pressure formula dynes/cm2
just audible sound .0002 dynes/cm2
loudest audible sound 2000 dynes/cm2
Acoustics The nature of sound and how it's measured The foundation for the testing of hearing.
Created by: schaunag



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