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Acoustic

Terms in this set (49)

sound
form or type of vibration that creates a wave and travels through a medium
two properties of sound are
physical and psychologically
physical events
can be physically measured
psychological phenomena
how sound is perceived -- can't be measured
physical properties of sound are
frequency, amplitude, and phase
psychological properties of sound are
pitch, loudness, quality
frequency goes to
pitch
amplitude goes to
loudness
phase goes to
quality
physical requirements for sound are
source of vibration, energy must create a disturbance in a medium that has mass and elasticity, and the disturbance moves away from sound source
Something to perceive sound is
an optional physical property of sound
compressions occur in
increased pressure
rare factions occur in
decreased pressure
1 cycle is equal to
one compression and one rare faction
Medium impacts the speed of sound
true
Transverse waves
motion of the molecules is perpendicular to the direction of the waves
Longitudinal
motion of the molecules is along the same axis as the wave - both moving in the same direction
Sine waves are
individual tones - waveform of a single frequency tone moves with simple harmonic motion
complex waves are
a sound made up of multiple frequencies - at least two frequencies
Frequency
changes in the rate of air molecule movement - number of cycles completed within one second
fast moving air molecules
high frequency/pitch
slow moving air molecules
low frequency/pitch
Hertz (Hz)
number of cycles per second (or frequency) - also called cycles (cps)
500 cycles per second is equal to how many Hz
500 Hz
Period
the amount of time it takes to complete 1 cycle
low frequency makes a ______ period
long
if the period changes so does
frequency
what type of relationship exists between period and frequency
reciprocal
Period =
1/frequency - ex. p=1/1000 p=0.001 sec
Humans can hear a range of
20-20000Hz
Amplitude
distance a mass moves (or is displaced) from its resting point
lower amp means
not moving as far
higher amps means
moving further/higher displacement
Peak amplitude
from resting point to highest point in compression
peak to peak amplitude
from the highest point of compression to the lowest point of rare faction
Intensity
the magnitude/strength of a sound
Loudness is the _________ of intensity
perception
Increase in ______ increases intensity
amplitude
Just audible sound is
20 micropascal
painful sound is
200000000 micropascal
to reduce the Hz range for humans we use the
decibel scale
Phase
stage of the cycle at any given point in time
Phase is measured with a
circle
Compression peak is always
90
rare faction peak is always
270
In phase
starting at the same point in cycle
out phase
starting at different point in cycles - when one starts at 0 another starts at 180
an example of out phase is
noise cancelling headphones
Complex waveforms
out of phase waves that are combined to make 1 wave
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