Overview of the Acoustic Parameters Flashcards
What is period?
The time it takes to complete 1 cycle
What is the symbol of period?
T
What are the units of period?
Time
- Microseconds
- Seconds
- Hours
- Days
What are the typical values of period?
0.06 microseconds to 0.5 microseconds
What is period determined by?
Sound source
Can period be adjusted?
No
What is the formula for period?
P (µs) = 1/f (MHz)
What is the relationship between period and frequency?
- Period and frequency are inversely related (Reciprocals) → If period gets longer, Frequency gets lower → If period gets short, Frequency gets higher
Period answers the question:
How long does it take for one cycle to occur? (Because the units of period is time)
What is frequency?
The # of cycles that occurs in 1 second
What is the symbol of frequency?
f
What are the units of frequency?
- Units per second
- Hertz
What are the typical values of frequency?
2MHz to 15 MHz (2 million hertz to 15 million per second)
What is frequency determined by?
Sound source
Can frequency be adjusted?
No
What is the formula for frequency?
- f (MHz) = 1/P (µs)
- f (MHz) = c (mm/µs) / λ (mm)
What is the relationship between frequency and wavelength
- Frequency and wavelength are inversely related → If frequency gets higher, Wavelength gets shorter → If frequency gets lower, Wavelength gets longer
- As frequency increases, Penetration is ____ and image quality/detail is ____
- As frequency decreases, Penetration is ____ ____, and image quality/detail is ____
- As frequency increases, Penetration is deeper and image quality/detail is higher
- As frequency decreases, Penetration is more shallow, and image quality/detail is less
Frequency answers the question:
How many cycles occur in 1 second? (Or ms, µs)
The bigness parameters describe:
Size, magnitude, and strength of a sound wave
The bigness parameters are:
- Amplitude
- Power
- Intensity
What is amplitude?
The difference between the average value of an acoustic variable and its maximum or minimum
What are the units of amplitude?
- Pressure— pascals (Pa)
- Density— kg/cm³
- Particle motion/distance— cm
- Relative term— dB
What are the typical values of amplitude?
1 million pascals (1 MPa) to 3 million pascals (3 MPa)
Amplitude is established by:
Sound source but attenuates as sound propagates through the body (depends of both sound wave and medium)
Can amplitude be adjusted?
Yes
What is the formula for amplitude?
- (Max amplitude - min amplitude) / 2
- Power ∝ Amplitude²
- Intensity ∝ Amplitude²
What is the relationship between power and amplitude?
- Power is proportional to amplitude squared
→ If amplitude increases by a factor, Power and intensity both increase by that factor squared
→ If amplitude decreases by a factor, Power and Intensity both decrease by that factor squared
What is the relationship between intensity and amplitude?
- Intensity is proportional to amplitude squared
→ If amplitude increases by a factor, Power and intensity both increase by that factor squared
→ If amplitude decreases by a factor, Power and Intensity both decrease by that factor squared
Increased amplitude =
Louder/Brighter echoes
Decreased amplitude =
Quieter/Darker echoes
What is power?
The rate of work or energy transfer
What is the symbol for power?
P
What are the units for power?
Watts
What are the typical values of power?
0.004 to 0.090 watts (4 to 90 milliwatts)
Power is determined by:
Sound source but attenuates as sound propagates through the body (depends of both sound wave and medium)
Can power be adjusted?
Yes
What is the formula for power?
- Power ∝ Amplitude²
- Power ∝ Intensity
What is the relationship between power and intensity?
- Power is proportional to intensity
→ If power increased by a factor, Intensity increases by the same factor (vice versa)
What is the symbol for intensity?
I
What is intensity?
The concentration of energy in a sound beam
What are the units for intensity?
watts/square centimeter, or W/cm² (watts from power and cm² from beam area)
What are the typical values of intensity?
0.01 to 300 W/cm²
Intensity is determined by:
Sound source but attenuates as sound propagates through the body (depends of both sound wave and medium)
Can intensity be adjusted?
Yes
What is the formula for intensity?
- Intensity ∝ Amplitude²
- Power ∝ Intensity
- I (watts/cm²) = P (watts) / Area (cm²)
What is the relationship between intensity and power and intensity and area?
- Intensity is directly related to power and inversely related to area
→ If intensity gets stronger, Power gets stronger OR area narrowed
→ If intensity weakens, Power weakens OR area gets wider
What is the symbol for wavelength?
λ (Lambda)
What is wavelength?
The distance or length of 1 complete cycle
What are the units of wavelength?
mm, meters, or any other unit of length
What are the typical values of wavelength?
0.1 to 0.8 mm
Wavelength is determined by:
Both the source and the medium
Can wavelength be adjusted?
No
What is the formula for wavelength?
- λ (mm) = c (mm/µs) / f (MHz)
- In soft tissue: λ (mm) = 1.54 (mm/µs) / f (MHz)
What is the relationship between wavelength and propagation speed?
- Wavelength and propagation speed are directly related → Wavelength gets longer, if speed increases
→ Wavelength gets shorter, if speed decreases
Wavelength answers the question:
How much space does a cycle take up?
What is the symbol for propagation speed?
c
What is propagation speed?
The rate at which sound travels through a medium
What are the units for propagation speed?
meters per second, mm/µs, or any distance divided by time
What are the typical values of propagation speed?
- 500 m/s to 4000 m/s
-
In soft tissue:
→ 1540 m/s, 1.54 mm/µs, 1 mile per second
Propagation speed is determined by:
Medium
Can propagation speed be adjusted?
No
What is the formula for propagation speed?
c = stiffness/ density
What is the relationship between speed and stiffness/bulk modulus?
- Speed and stiffness/bulk modulus are directly related
→ If a medium is stiffer, Speed is faster
→ If a medium is more compressible/elastic, speed is slower
What is the relationship between speed and density?
- Speed and density are inversely related
→ If a medium is more dense, Speed is slower
→ If a medium is less dense, Speed is faster
Propagation speed answers the question?
How fast does speed travel through a medium?
