physical quantity with vibration - periodic or aperiodic - and a pressure disturbance - compressions and rarefractions - and a medium - material for transmitting the sound
periodic
regularly repeating
ex) tone
repeats the same frequency
aperiodic
not reguarly repeating
2 types - turbulent and static
ex) noise, bullistic, release of stop consonants
Simple Harmonic Motion
tuning fork
produces the simpliest type of sound
tine movement : X-Y-X-Z-X-Y-X-Z-X
one cycle: X-Y-X-Z-X
Period / frequency
amount of time for one cycle / # cycles per second
frequency = 1/period or f=1/T
physical dimension - observable and measurable
Hz
pitch
the perception of frequency
relationship between frequency/period and pitch
increase in frequency = increase in pitch
not a 1:1 change/dimension
same physical change does not equal the same perceptual change
amplitude
force or pressure of sound
related to displacement of tine
loudness
perception of amplitude
decibel dB
relationship between amplitude and loudness
increase in amplitude = increase in loudness
not a 1:1 dimension
Simple Harmonic Motion
Uniform Circular Motion
another type of SHM
circle of radius r
point P moves around circle at a uniform speed
at each new P, a new radius r' is drawn that forms an angle (theta) with the original r
by the time P goes around the circle, theta will go from 0 to 360 degrees
phase refers to
the angle of theta
period
time for one revolution
frequency
# cycles/second
amplitude
the radius of the circle
Amplitude (X) varies with
the sine of theta
X = r * sine
waveform
graph of displacement as a function of time
the waveform associated with SHM is the sine wave because the formula contains the sine function
spectrogram includes
time
amplitude
frequency
spectrum includes
amplitude
frequency
Simple Harmonic Motion
Pendulum
velocity is zero / movement stops at the extremes
velcoity is at its max at the point of rest
amplitude graph vs. velocity graph
the amplitude graph is alays 90 degrees behind the velocity graph
superpositioning of sound waves
adding sine waves together
go point by point on the x axis and add the y axis numbers together
adding sine waves of equal frequency results in
a sine wave with the same frequency
creates simple waves
adding sine waves of different frequencies results in
complex waves - any wave that is not a sine wave
a wave with more than one frequency component
square waves are formed by
adding the odd multiples of a given frequency
the fundamental frequency is
the lowest frequency
largest comon multiple in a series of frequencies
harmonics
frequencies that are integer multiples of the fundamental frequency