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Distance and circumfrence is measured in?
feet, meters, inches
Area is measured in?
square feet
Volume is measured in?
cubes (^3)
What the tissue is doing to the sound wave?
acoustic propagation properties
Must have one of these three things to be a sound wave.
acoustical variables (pressure, density, distance)
Acoustical variables must be happening?
rhythmically
The three acoustical variables?
Pressure (Pretty)
Density (Dang)
Distance (Dumb)
Concentration of force within an area?
pressure
Pressure is measured in?
pascals (Pa)
Concentration of mass within a volume (^3)?
density
Unit of desity?
kg/cm^3
Measure of particle motion?
distance
Sound is ____________ energy.
mechanical (longitudinal)
Sound is comprised of?
compressions & rarefractions
Areas of increased pressure and density?
compressions
Areas that have decreased pressure and density?
rarefractions
Sound only travels?
in a straight line
Particles moving perpendicular to the direction of the wave?
transverse wave
Particles moving parallel to the direction of the wave?
longitudinal wave
The time it takes to complete a single cycle?
period
Unit of a period?
microseconds
Typical values of a period?
0.06-0.5 microseconds
A period is determined by the?
sound source (p)
Can a sonographer change the period?
No (p)
The number of cycles of an acoustic variable that occur in one second?
frequency
Unit of frequency?
per second (hertz)
Typical values of frequency?
2-15 MHz
Frequency is determined by the?
sound source (f)
Can a sonographer change the frequency?
No (f)
Smaller frequency =
more penetration
How are frequency and period related?
inversely
Period and frequency are?
reciprocals
Period = 1/frequency
Frequency = 1/period
High frequency =
low period
High period =
low frequency
Anything greater than 20,000 Hz is classified as?
ultrasound
Anything between 20-20,000 Hz is classified as?
audible sound
Anything below 20 Hz is classified as?
infrasound
Define amplitude
the difference between the average value and the maximum or minimum value of an acoustic variable
Unit of amplitude?
decibels (dB)
Amplitude is determined by?
sound source (initially) (a)
Can amplitude be changed by the sonographer?
yes (a)
Peak-to-Peak amplitude
the difference between the maximum & minimum values in an acoustic variable
The rate at which work is performed or the rate of energy transfer
power
Unit of power?
watts (W)
Power is determined by the?
sound source (initially) (pr)
Can power be changed by the sonographer?
yes (pr)
Power is __________ to amplitude squared.
proportional
P= (A)^2
Concentration of energy in a sound beam?
intensity
Unit of intensity?
W/cm^2 (power/beam area)
Intensity and power are?
proportional
Typical values of intensity?
0.001-100 W/cm^2
Intensity is determined by the?
sound source (initally) (i)
Can intensity be changed by the sonographer?
Yes (i)
Intensity is proportional to
amplitude squared
I= (A)^2
As amplitude goes up by 4, intensity ______
goes up by 16
Audible sound range
20-20,000 Hz
Audible sound = _________ kHz
0.02-20 kHz
Below ______ Hz is infrasound.
20 Hz
Intensity = ______ /______
power/beam area