The Electronic Device & Transducer
System is changed by?
Selecting a different transducer
What parameters of sound can't be adjusted w/o changing the system?
Frequency & Wavelength
What 4 factors can be changed
PRP, Duty Factor, Listening Time, Amplitude
What is a graph?
A diagram representing data and relationships between data
What is related?
Relationship between two items
i.e Transducer Frequency and Depth
High Frequency attenuates?
What is unrelated?
Absence of a relationship between two items.
Why are Frequency and propagation speed unrelated?
Speed is controlled by the medium.
Frequency is controlled by crystal thickness.
2 factors that affect propagation speed
Density and Stiffness
When one item increases, the other also increases.
Crystal Diameter and Focal Length
Frequency and Focal Length
When one item increases, the other decreases
Frequency and Wavelength
Frequency and Period
Multiplying two items is equal to one
i.e 10 and 1/10 are reciprocals
T = 1/f
Period and Frequency
Megahertz in Frequency compliments
Microseconds in Period
Millimeters or Microseconds in Speed compliments
Megahertz in Frequency
Frequency in Hertz compliments
Period in Seconds
3M's go together
MHz, mm, us
H, m, s go together
Hz, m, s
If Period is in seconds
Frequency must be in cycles/sec or Hz
If Wavelength is in mm and Propagation speed is in mm/us
Frequency will be in MHz
Difference between mm and ml
mm is distance
ml is volume
How many mm in 1cm
How many cm in 1m
How many us in 1s
What is Hz
How many KHz in 1MHz
What is the Period of a wave with a 10MHz Frequency
What is the Frequency of a wave with a .1us Period
5 Characteristics of a Sound Wave
1.Mechanical Wave 2.Longitudinal Wave 3.Travels in a straight line 4.travels through a medium 5.Composed of Compression and Decompression
Travels in a direction parallel to the direction of sound propagation.
Sound Wave composition
Compression and Decompression
Decompression is AKA
High pressure area in the medium
Low pressure area in the medium
2 Biological effects of Ultrasound
Mechanical and Thermal
Changes that propagating sound produces in the medium
Things that oscillate in a sound wave
List the 4 Acoustic Variables
The concentration of force
(force/area) Unit: lb/sq in or Pascal (Pa)
Concentration of mass
(Mass/Volume) Unit: Kg/cu.cm
Concentration of heat energy
Unit: Degrees Centigrade
Measure of particle motion
Unit: cm or mm
Factors used to describe the characteristic of a sound wave
List the 7 Acoustic Parameters
7. Propagation Speed
Particles move in a perpendicular direction of the sound propagation.
Different waves lose their individual characteristics and combine to form a single wave
Two in-phase waves combine to form a larger single wave.
Two out-of-phase waves combine to form a smaller single wave.
Things that we use can use to classify sound
Time it takes to create one cycle or sound wave.
Units: s, ms, us
0.1 - 0.5us
Period is determined by what sound source? Is Period adjustable?
Is Period determined by the medium?
No. By the Transducer
How are Period and Wavelength related?
Frequency Value Range
What does Frequency have an important effect on?
Depth and image quality (Resolution)
Less than 20Hz
Audible Sound Range
Greater than 20,000Hz
With intensities 0.25W/sq.cm-2.5 W/sq.cm
High Intensity Focused Ultrasound- destroys tumors using 0.5MHz-10MHz, with intensities as high as 1500w/sq.cm
What is the relationship between Period and Frequency?
Reciprocal Inverse Relationship
If the Period PF a wave is 1/8sec, what is the Frequency?
8 cycles/sec (c/s)
Period increases when what decreases?
If one remains constant the other remains?
What 3 Parameters describe the strength of a sound wave?
Power, Intensity, Amplitude
Between the MAX value and the average or undisturbed value of an acoustic variable
Between the MIN value and the average or undisturbed value of an acoustic variable
A Measurement of signal strength is?
What units are used for Amplitude?
Pressure-Pascals (only if lbs/sq.in)
Amplitude Pressure Value Range
1-3 million Pascals
How do you adjust Amplitude?
By changing the power
Amplitude is determined by?
The rate of energy transfer
Units: Watts or Milliwatts (mw)
it also adjustable.
Power Value Range
4-90 mw or .004-0.90 Watts
Power is determined by?
Relationship between Amplitude and Power
Power is Proportional to?
If Amplitude is decreased to 1/2 of it's original value?
Power is decreased to 1/4 of it's original value
Concentration of energy in the sound beam
Intensity Value Range
Intensity is determined by?
The Sound Source
Relationship between Power and Intensity
If a wave's Power is doubled?
The Intensity is doubled (if the Area is not changed)
Relationship between Intensity and Amplitude
Proportional to the wave's Amplitude squared
If a wave's Amplitude is doubled?
The Intensity is quadrupled
The length of one complete cycle
Units: mm, m
Wavelength Value Range
The only Parameter Determined by?
Sound Source and Medium
Calculate the Wavelength for a 2MHz Transducer
1540m/s divided by 2,000,000s=.00077m
Relationship between Wavelength and Frequency
If Frequency is Doubled?
Wavelength is halved
Shorter Wavelength sound produces?
A higher quality image w/ greater details
Distance Sound Wave travels through a Medium
Units: mm/us, km/s, m/s
Propagation Speed Value Range
1.54mm/us or 1540m/s
Propagation Speed is Determined by?
Propagation Speed Formula
c(m/s) = f(Hz) x wavelength(m)
Factors that effect Propagation Speed
Stiffness and Density
Ability to resist pressure, and Directly Proportional to Speed
mass/volume, and Inversely Proportional to Speed
5 Propagation Speeds
Soft Tissue; 1,540m/s
Blood and Liver; 1,560m/s
Can adult Lungs be scanned?
No. Only Fetal Lungs, because the are filled with blood
What 3 Parameters describe the strength or magnitude of sound?
Power, Intensity, Amplitude
What Parameter is determined by both the sound source and the medium?
What Parameter is determined only by the Medium?
What 2 Parameters are reciprocals?
Period and Frequency
What is the Wavelength of 1MHz sound wave in soft tissue?
What 2 Parameters can be measured using the same parts of a sound wave?
Wavelength and Period
What is the difference between Speed and Velocity?
Velocity has a vector
What Medium will most likely have the fastest propagation speed for sound?
What Medium will reflect more sound waves?
What Medium will transmit more sound waves?