Ch. 3 Physics: Describing sound waves Flashcards
What is the source of a sound wave?
The ultrasound system and the transducer
What is considered the medium which sound travels through?
Body Tissue, Gel, or the organs
What is the time from the start of one cycle to the start of the next?
Period
What is the units of mesurement for period?
Millisecond
seconds
What is the typical value for period?
.06 to .5 microseconds
What is the period determined by?
The sound source
Is the period adjustable or not adjustable by the sonographer?
Not adjustable
What is the number of complete cycles in one second?
Frequency
What is the unit of measurements for Frequency?
Hertz (Hz)
What is the clinical value range for frequency?
2 to 15 MHz
What is frequency determined by?
the Sound source
Is the frequency adjustable or not adjustable by the sonographer?
Not adjustable
What is the sound frequency for audible sound?
20Hz to 20kHz
What is the sound frequency for infrasound?
below 20Hz
What is the sound frequency for ultrasound?
Greater than 20kHz
True or False:
Frequency of sound is clinically important since it affects penetration and image quality.
True
What produces better image quality?
Higher frequency, less penetration
What produces lesser image quality?
Lower frequency, More penetration
What is the relationship between period and frequency?
Inversely
As frequency increases, what will happen to the period?
Will decrease
As frequency decreases, what will happen to the period?
will increase
What is the period of wave that has a frequency of 8Hz?
1/8 of a second
What is the 3 bigness parameters?
Intensity
Power
Amplitude
What can Amplitude also be expressed as?
Decibels (db)
The “bigness” of a given wave either above the baseline or below the baseline.
Amplitude
Clinically, pressure amplitude ranges from what?
1 million pascals (1MPa) to 3 million pascals (3 MPa)
Amplitude is determined by what?
the sound source
True or False:
Amplitude increases as it propagates through the body
False
it decreases
How is amplitude measured?
from the baseline out to the peak.
Is amplitude adjustable or not adjustable by the sonographer?
Adjustable
The ratee of energy transfer, or the rate at which work is done is called what?
Power
What is the unit of measure for power?
watts
Clinically, what is the imaging values range for power?
0.004 to 0.090 watts
What is power determined by?
the sound source
Does power decrease or increase as it propagates through the body?
Decrease
Is power adjustable or not adjustable by the sonographer?
Adjustable
True or False:
Power is affected by the density of the medium
True
What is the relationship of power and amplitude?
Directly related or directly proportional
When power increases, what happens to the amplitude?
it increases
When power decreases, what happens to the amplitude?
it decreases
What is the concentration of energy in a sound beam called?
Intensity
What are the units for intensity?
Watts/square centimeter (W/cm^2)
True or false:
Intensity depends on the power of the beam and the area over which the power is applied.
True
What is the value range for intensity?
0.01 to 300 W/cm^2
What is instensity determined by?
the sound source
Intensity sound propagation chages depending on the characteristics of what?
Both the sound wave and the medium
Is intensity adjustable or not adjustable by the sonographer?
Adjustable
What is the relationship between intensity and power?
It is proportional
What is the relationship between intensity and amplitude?
it is proportional
If the power of a wave doubles, the intensity…
also doubles
If the power of a wave is cut in half, the intensity is….
also cut in half
Always remember that squared follows…
amplitude
The distance or length of one complete cycle is called
wavelength
What is the units of measure for wavelength?
mm, meters
Clinically, the wavelength in soft tissue ranges from…
0.15 to 0.8mm
what is the wavelength determined by?
Both source and medium
Is the wavelength adjustable or not adjustable by the sonographer?
Not adjustable
What is the relationship between wavelength and frequency?
inversely
In soft tissue, sound with a frequency of 1MHz has a wavelength of…
1.54mm
If the wavelength goes up, the frequency..
goes down
If frequnecy goes up, the wavelength..
goes down
How do you determine the wavelength in soft tissue?
Divide 1.54mm by the frequncy in MHz
What is the wavelength using a 1MHz transducer?
1.54mm
What is the wavelength using a 2MHz transducer?
.77mm
Higher frequency = _______ wavelengths
shorter
Lower frequency =________ wavelengths
longer
Which frequency will have better image quality?
High frequency
Which frequency will penetrate deeper?
Low frequency
What is the rate at which a sound wave travels through a medium called?
Propagation Speed
What is propagation speed measured in?
mm/s or distance/time
What is propagation speed dependent on?
Tissue
What is the speed range for propagation speed?
500 m/s to 4000 m/s
Propagation speed is determined only by what?
the medium
Is propagation speed adjustable or not adjustable by the sonographer?
Not adjustable
True or false:
All sound travels at different speed
False
travels at the same speed
What is the speed of sound in soft tissue?
1540 m/s or 1.54km/s or 1.54mm/µs
Does sound travel slow or fast in solids?
Fastest
Does sound travel slow or fast in liquids?
Slower
Does sound travel slow or fast in gasses?
Slowest
What are the 7 acoustic parameters?
Period
Frequency
Amplitude
Power
Intensity
Wavelength
Speed
What determines the speed of period and frequency?
Sound source
What determines the speed of amplitude, power and intensity?
Sound source
What determines the speed of wavelength?
sound source and medium
What determines speed?
Medium
What is the ability of an object to resist compression called?
Stiffness
What is directly related to speed?
Stiffness
What is another term for stiffness?
Bulk Modulus
What is the opposite of stiffness?
Elasticity and compressibility
What describes the relative weight of a material?
Density
True or false:
Dense material wighs more than non-dense.
True
What is related to density?
Weight
What relationship do density and speed have?
inversely related