Ch. 3 Describing Sound Waves Flashcards
______________________ describe features of a sound wave.
Parameters describe features of a sound wave
___________________ is the time is takes a wave to vibrate a single cycle, or the time from start of one cycle to the start of the next cycle.
Period is the time it takes a wave to vibrate a single cycle, or the time from start of one cycle to the start of the next cycle.
Units for Period:
units for period are units of time, such as microseconds, seconds, hours, or days
Typical Values for Period:
0.06 to 0.5 microseconds
Period is determined by:
Can it be changed?
period is determined by the ~sound source
~ & Cannot be changed
______________________ is the number of particular events that occur in a specific duration of time.
frequency is the number of particular events that occur in a specific duration of time
In diagnostic ultrasound, the _______________________ of a wave is described as the number of cycles that occurs in one second
In diagnostic ultrasound, the frequency of a wave is described as the number of cycles that occurs in one second
Units for frequency:
per second, 1/second, hertz, or Hz
1 cycle/second =
1 hertz
1,000 cycles/second =
1 kHz
1,000,000 cycles/second =
1 MHz
In clinical imaging, frequency ranges from approximately ___ MHz to ________ MHz
In clinical imaging, frequency ranges from approximately 2MHz-15MHz
Frequency is determined by the:
sound source
frequency is __________ adjustable
Frequency is NOT adjustable
Infrasound:
Sound waves with frequencies below 20 Hz.
Audible Sound:
sound waves between 20 Hz and 20,000 Hz (20 kHz)
Ultrasound:
Sound waves with frequencies above 20,000 Hz (20KHz).
What is the relationship between frequency and period?
They are inversely related
They have an even more special relationship that is called reciprocal
As frequency increases, period ____________________
As frequency increases, period decreases
As frequency decreases, period ___________________
As frequency decreases, period increases
What is the period of the earths rotation around the sun?
A. 1 day
B. 1 hour
C. 1 month
D. 1 year
D. the earth completes one cycle around the sun in one year
A top in spinning on a table. What is the period of the spinning top?
A. 4 pounds
B. 8 dollars
C. 0.05 seconds
D. 3cm
C. of the available answers, the only one that has units of time is 0.05 seconds. This must be the answer
Which of the following waves is infrasonic?
A. 4 Mhz
B. 400 kHz
C. 28 Hz
D. 2 Hz
D. A wave with a frequency less than 20 Hz cannot be heard because its frequency is less than the lower limit of human hearing
Identify the wave that is ultrasonic.
A. 400 mHz
B. 4 MHz
C. 28 Hz
D. 2 Hz
B. A wave with a frequency greater than 20,000 Hz cannot be heard because its frequency is higher than the upper limit of human hearing
Which of these waves is ultrasonic and most useful in diagnostic sonography?
A. 400 MHz
B. 4 Mhz
C. 2 kHz
D. 200,000 Hz
B. although choices A, B, and D are all ultrasonic, only B falls within the typical range of frequencies used in diagnostic sonography
Identify all the waves that are inaudible (more than 1 answer may be correct)
A. 4 Mhz
B. 400 kHz
C. 28 Hz
D. 2 Hz
A, B, and D. These 3 waves are inaudiable and cannot be heard by humans. Choices A and B are ultrasonic, wheres D is infrasonic. Humans cannot hear infrasound or ultrasound
Which of the following waves has the longest period?
A. 2 MHz
B. 4,000 Hz
C. 6 Hz
D. 1 kHz
C. the wave with a frequency of 6 Hz has the longest period. Period and frequency have an inverse relationship. Thus, the wave with the lowest frequency has the longest period
Of the four waves whose frequencies are listed below, which has the shortest period?
A. 12 kHz
B. 6,000 Hz
C. 205 Hz
D. 1 kHz
A. Of the 4 choices, A has the highest frequency and thus, the shortest period.
Of the four waves whose periods are listed below, which has the lowest frequency?
A. 8s
B. 80 us
C. 8Ms
D. 800ks
C. The wave with the longest period has the lowest frequency. Choice C has a period of 8 million seconds 8Ms, which is the longest period
The three “bigness” parameters are _______________________, _____________________, and ______________________
The three “bigness” parameters are amplitude, power, and intensity
__________________________ is the “bigness” of a wave. It is the difference between the maximum value and the average or undisturbed value of an acoustic variable.
amplitude is the “bigness” of a wave. It is the difference between the maximum value and the average or undisturbed value of an acoustic variable
________________________ can also be the difference between the minimum value and the average value of the acoustic variable
amplitude can also be the difference between the minimum value and the average value of the acoustic variable
Amplitude can have units of any of the acoustic variables such as __________________, ____________________, and ____________________ ___________________
Amplitude can have units of any of the acoustic variables such as pressure Pascals, density g/cm^3 and particle motion cm, inches, any distance and *decibels
Typical Values for amplitude are:
1 million pascals (MPa) to 3 million pascals (MPa)
Amplitude, in relative terms, can also be expressed in decibels (dB)
Amplitude is determined by:
the sound source
Is amplitude adjustable?
Initial amplitude is, yes.
What is the difference between amplitude and peak-to-peak amplitude?
amplitude is measured from the middle, or undisturbed, value to maximum value.
peak-to-peak amplitude is the difference between maximum and minimum values of an acoustic variable. Therefore peak-to-peak is twice the value of the amplitude.
______________ is the rate of energy transfer or the rate at which work is performed.
power is the rate of energy transfer or the rate at which work is performed
What are the units for power?
Watts (W)
Typical values for Power range from _______ to ________ milliwatts
Typical values for power range from 0.004 to 0.090 watts (4-90 milliwatts)
Power is determined by the:
sound source
Is power adjustable by the sonographer?
Yes, initial power can be changed.
When you think of Power, it helps to think of a _______________ ______________
When you think of power it helps to think of a light bulb
Power is proportional to _____
amplitude squared
If a sonographer increases the amplitude of a wave by the factor of 3. How does the power change?
Recall that power is proportional to the amplitude squared:
3 times 3 = 9
Thus the power is increased 9-fold. In other words, if the amplitude is increased by a factor of 3, the power is increased by a factor of 9
______________________ is the concentration of energy in a sound beam.
Intensity is the concentration of energy in a sound beam
Intensity formula:
I (W/cm^2) = P (w) /A (cm^2)
Intensity is determined by the:
sound source
Is intensity adjustable by the sonographer?
Yes, initial intensity, like power and amplitude, can be adjusted by the sonographer.
Intensity is ____________________ to power
proportional
If a waves power is doubled, intensity is _______.
doubled
Intensity is ______________ to amplitude squared
Intensity is proportional to amplitude squared
_________________________ is the distance or length of one complete cycle.
wavelength is the distance or length of one complete cycle
What are the units for wavelength?
meters (m) or millimeters (mm) or any other unit of length
Wavelength is determined by
Both the source and the medium
Is wavelength adjustable by the sonographer?
No, wavelength cannot be changed by the sonographer when using basic ultrasound transducer
______________________ is the only parameter that is determined by both the source and the medium
wavelength is the only parameter that is determined by both the source and the medium
What is the relationship between wavelength and frequency?
As long as a wave remains in one medium, wavelength and frequency are inversely related. As frequency increases, wavelength decreases. The lower the frequency, the longer the wavelength.
_____________________ _____________ is the rate at which a sound wave travels through a medium
propagation speed is the rate at which a sound wave travels through a medium
what are the units for propagation speed?
Speed is measured in units of meters per second, mm/us, or any distance divided by time.
What are the typical values for propagation speed?
In the body, the speed of sound ranges from 500 m/s to 4000 m/s depending on the tissue through which it is traveling
Propagation speed is determined by
Medium only - density and stiffness
Is propagation speed adjustable by the sonographer?
No, speed of sound cannot be changed by the sonographer. Speed changed only when the wave travels from one medium to a different medium
Speed of sound in soft tissue
1540 m/s, 1.54 mm/us, 1.54 km/s
What is the propagation speed for lung:
500 m/s
What is the propagation speed for Fat:
1,450 m/s
What is the propagation speed for Soft tissue:
1,540 m/s
What is the propagation speed for Liver:
1,560 m/s
What is the propagation speed for Blood:
1,560 m/s
What is the propagation speed for Muscle:
1,600 m/s
What is the propagation speed for Tendon:
1,700 m/s
What is the propagation speed for Bone:
3,500 m/s
What is the speed of sound in air?
330 m/s
What is the speed of sound in water?
1,480 m/s
What is the speed of sound in metals?
2,000 to 7,000 m/s
What two characteristics affect the speed of sound?
- stiffness
- density
______________________ describes the ability of an object to resist compression. In other words, what will happen if the material is squeezed?
stiffness describes the ability of an object to resist compression. A stiff material will retain its shape, whereas a non-stiff material will change its shape.
____________________ describes the relative weight of a material.
density describes the relative weight of a material. When equal volumes of two materials are compared, the dense material weighs a lot, whereas the non-dense material weighs little.
Stiffness and speed are ______ related.
directly; when Stiffness increases, Speed increases
Density and speed are ___________ related
inversely; when density increases, speed decreases
What are the units of:
- wavelength
- frequency
- intensity
- propagationspeed
- period
- power
Wavelength = millimeters
Frequency = hertz
Intensity = watts/cm^2
Propagation Speed = meters/second
Period = second
Power = watts
Does the medium or the sound source determine these parameters:
- wavelength
- frequency
- intensity
- propagation speed
- period
- power
- amplitude
Wavelength - determined by both sound source & medium
Frequency - determined by sound source
Intensity - determined by sound source
Propagation Speed - determined by medium
Period - determined by sound source
Power - determined by sound source
Amplitude - determined by sound source
Using a particular ultrasound system and transducer, which of the following cannot be changed by the operator?
- wavelength
- frequency
- intensity
- propagation speed
- period
- power
- amplitude
Wavelength cannot be operator changed
Frequency cannot be operator changed
Intensity can be changed by the operator
Propagation Speed cannot be operator changed
Period cannot be operator changed
Power can be changed by the operator
Amplitude can be changed by the operator
