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Length or distance of a single cycle
Wavelength
Unit for wavelength
Millimeters
Typical values for wavelength
.1-.8mm
Wavelength is determined by
Sound source and medium
Can wavelength be changed by sonographer
No
How are wavelength and frequency related
Inversely
Higher frequency=
Shorter wavelengths
Lower frequency=
Higher wavelengths
The rate that sound travels through medium
Propagation speed or speed of sound
Propagation speed units
Distance/time Mm/no
Typical value for propagation speed
1500-1600 meters per second
What is propagation determined by
Medium only
Can propagation speed by changed by sonographer
No
Air
330m/s
Lung
500m/s
Fat
1450 m/s
Soft tissue (average)
1,540m/s
Liver
1,550m/s
Kidney
1560m/s
Blood
1570m/s
Muscle
1600m/s
Tendon
1850m/s
Bone
3500m/s (2000-4000)
How are speed and wavelength related (7)
Directly related (7)
Sound in slow medium has ______ wavelength
Short
Sound in fast medium has _____ wavelength
Long
Two characteristics of medium that affect the speed of sound
Stiffness Density
How are density and speed related (8)
Inversely related (8)
Change in shape, ability of an object to resist compression
Stiffness
Describes the relative weight of a material
Density
Can make the biggest change
Stiffness
What can have the greatest effect on speed
Stiffness
What relationship does speed and stiffness have
Direct
Other words for density
Compressibility Density Elasticity
Bulks relationship with speed
Direct (not the same as stiffness but has the same effect on speed)
If stiffer=
Goes faster
If denser=
Goes slower
The higher the frequency=
The less penetration
Amplitude =
Squared
If the amplitude of a wave is increased to 3 times its original value, the intensity is increased by 6 times (True or false)
False would be 9
Does propagation do anything to frequency
No
Acoustic variables
Density Particle motion Pressure (Pretty dang dumb)
What will create the fastest speed of sound
Low density, high stiffness
When two waves overlap at the same location and at the same instant in time, they combine with each other. The result of overlap is the creation of a single, new wave
Interference
In phase
Constructive interference
Out of phase
Destructive interference
When peaks and troughs come together opposite times they cancel out and make a smaller wave
Destructive
When the amplitude is less than one of the original two waves
Out of phase
Any number represents the number "10s" that are multiplied together to create the original number
Logarithms
Comparing a new intensity to original
Logarithmic scale
Log of 100
2
Log of 1000
3
_____dB means two
3
The final intensity is twice as big as the original intensity
3dB
The final intensity is 4 times the original
6dB
The final intensity is 8 times the original
9dB
The final intensity is 10 times bigger than the original intensity
10dB
The final intensity is 100 times bigger than the original
20dB
If using negative number new intensity will be _______ than original
Smaller
Fallen to 1/2 the original value
-3dB
Means we have fallen to 1/4 original intensity
-6dB
Means we have fallen to 1/8 of the original value
-9dB
We have fallen to 1/10 of the original value
-10dB
We have fallen to 1/100 of the original value
-20dB
How many intensities do we need to calculate decibels
2 intensities
A single power increases from 1 watt to 100 watts. How is this expressed in decibels?
20dB
An ultrasound system is operating at 100% power and the power setting is 0dB. What would the power setting be when the system is operating at 50%
-3dB
A sound beam has increased from its initial intensity by a factor of 100. How is this described in decibel notation?
20dB
DB is a mathematical representation with a _______ scale
Logarithmic
The relative CHANGE in a sound beams intensity is measured in
Db
Intensity unit
Watts/cm^2
The decrease in intensity, power, and amplitude as sound travels
Attenuation
Further sound travels the ________ it gets
Weaker
Attenuation units
DB
Frequency and attenuation have what relationship (5)
Direct (5
Path length and attenuation have what relationship (3)
Direct (3)
Higher the frequency the ________ attenuation
More
More frequency travels _________ they attenuate
More
High frequency =
More attenuation Long pathway
For less attenuation you want
Short pathway Low frequency
For more attenuation you want
High frequency Long pathway
A 3MHz sound beam travels through two media. It attenuates 5dB in medium A and 6 dB in medium B. What is the total attenuation that sound beam undergoes as it travels through both media
11dB
3 processes that contribute to attenuation
Reflection Scattering Absorption
Sound dissipated in heat
Absorption
As sound strikes a boundary, a portion of the wave's energy may be redirected, or reflected, back to the sound source
Reflection
2 types of reflection
Specular & Diffuse
Back scatter
Diffuse
Reflectors form a smooth reflector (mirror) are specular and return in ONE direction
Specular
Occurs when the wavelength is much smaller than the irregularities in the boundary
Specular reflection
When are specular reflectors well seen
When the sound wave strikes the reflector at 90 degrees
Examples of specular boundaries
Diaphragm Walls of vessels
What is best for grey scale
90
When boundary is rough, reflected sound is disorganized and random (1)
Diffuse reflection (1)
Occurs when the boundary has irregularities that are approximately the same size as the sound's wavelength (6)
Diffuse reflection (6)
The distribution of sound randomly in all directions
Scattering
When does sound scatter
When the tissue interface is small; that is, equal to or less than the wavelength of the incident sound beam
Which sound beams scatter more
High frequency
If reflector is much smaller or wavelength is bigger
Raleigh scattering
Omni directional
Raleigh scattering
Rayleigh and frequency relationship
Proportional
Note 
Flashcard (25)