PHYSICS: CH 3 Sound Waves
______________________ is the concentration of energy in a sound beam.
*Intensity* is the concentration of energy in a sound beam
The effects of a medium on an ultrasound wave are called _____.
acoustic propagation properties
The effects of tissue on sound waves are called _____.
acoustic propagation properties
Density and speed are ___________ related.
inversely; when density increases, speed decreases
Frequency is determined by the:
sound source
Intensity is determined by the:
sound source
Power is determined by the:
sound source
Units for Period:
units for period are units of time, such as microseconds, seconds, hours, or days
True or False? Lower frequency sound creates higher quality images with greater detail
False. Frequency plays a very important role in image quality. Higher frequency sound usually produces higher quality images with greater detail
True or False? With standard ultrasound pulses, the frequency of the ultrasound changes significantly as the wave propagates through the body.
False. In diagnostic imaging, the frequency of the sound wave generally remains constant and does not routinely change as the sound propagates through the body. Slight changes occur when sound strikes moving structures.
True or False. If the amplitude is a wave is increased to 3 times its original value, the intensity is increased by 6 times
False. Intensity is proportional to the amplitude squared. If we triple the amplitude, we increase the intensity by a factor of nine.
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
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
Is amplitude adjustable?
Initial amplitude is, yes.
Intensity is ______________ to amplitude squared
Intensity is *proportional* to amplitude squared
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
Is wavelength adjustable by the sonographer?
No, wavelength cannot be changed by the sonographer when using basic ultrasound transducer
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
Ultrasound:
Sound waves with frequencies above 20,000 Hz.
Infrasound:
Sound waves with frequencies below 20 Hz.
what are the units for propagation speed?
Speed is measured in units of meters per second, mm/us, or any distance divided by time.
The three "bigness" parameters are _______________________, _____________________, and ______________________
The three "bigness" parameters are *amplitude*, *power*, and *intensity*
True or False? A sonographer can routinely change the power of a wave emitted by a transducer used in diagnostic ultrasonic imgaing
True. A sonographer can alter the power of an ultrasound wave by adjusting a control on the ultrasound system. Power and amplitude are related; if the amplitude is increased, then so is the power. When the amplitude decreases, the power also decreases.
Is intensity adjustable by the sonographer?
Yes, initial intensity, like power and amplitude, can be adjusted by the sonographer.
Is power adjustable by the sonographer?
Yes, initial power can be changed.
Power is proportional to _____
amplitude squared
Audible Sound:
sound waves between 20 Hz and 20 kHz
What is the propagation speed for Bone:
3,500 m/s
Wavelength is determined by
Both the source and the medium
frequency is __________ adjustable
Frequency is NOT adjustable
What is the propagation speed for Blood:
1,560 m/s
What is the propagation speed for Liver:
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
Units for frequency:
Frequency is reported in units of per second, 1/second, hertz, or Hz. Hertz is another way to say per second
______________________ 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.
________________________ 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
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 "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
____________________ 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.
______________________ 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
______________ 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
_____________________ _____________ 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
______________________ 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.
_________________________ is the distance or length of one complete cycle.
*wavelength* is the distance or length of one complete cycle
______________________ 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
How are the following parameters related - directly, inversely, or unrelated? - frequency and period - amplitude and power - amplitude and intensity - power and intensity - wavelength and intensity - wavelength and frequency - acoustic velocity and density - elasticity and speed of sound - acoustic velocity and compressibility - stiffness and sound speed - frequency and sound speed - frequency and intensity - power and frequency
- frequency and period = inversely - amplitude and power = directly - amplitude and intensity = directly - power and intensity = directly - wavelength and intensity = unrelated - wavelength and frequency = inversely - acoustic velocity and density = inversely - elasticity and speed of sound = inversely - acoustic velocity and compressibility = inversely - stiffness and sound speed = directly - frequency and sound speed = unrelated - frequency and intensity = unrelated - power and frequency = unrelated
What two characteristics affect the speed of sound?
- stiffness - density
Typical Values for Period:
0.06 to 0.5 microseconds
1,000,000 cycles/second =
1 MHz
1 cycle/second =
1 hertz
1,000 cycles/second =
1 kHz
Typical Values for amplitude are:
1 million pascals to 3 million pascals
What is the propagation speed for Fat:
1,450 m/s
What is the speed of sound in water?
1,480 m/s
What is the propagation speed for Soft tissue:
1,540 m/s
Speed of sound in soft tissue
1540 m/s, 1.54 mm/us, 1.54 km/s
What is the speed of sound in metals?
2,000 to 7,000 m/s
What is the speed of sound in air?
330 m/s
What is the propagation speed for lung:
500 m/s
Which of the following units are appropriate to describe the period of an acoustic wave? (more than one answer may be correct) A. minutes B. microseconds C. meters D. millimeters/microseconds E. cubic centimeters
A and B The period of a wave is defined as the time that elapses as a wave oscillates through a single cycle. The units for period must be a measure of time, such as minutes or seconds. A and B are units of time. The incorrect selections C, D, and E are units of distance, speed, and volume, respectively.
Which of the following are acceptable units for the amplitude of an acoustic wave? (more than one answer might be correct) A. cm B. pascals C.gauss D. watts
A and B The acoustic variables are pressure, density and particle motion. The units of acoustic wave amplitude are cm for particle motion and pascals for pressure.
Which of the following are considered acoustic parameters? A. frequency B. density C. distance D. pressure E. period
A and E
A particle within a transverse wave is traveling vertically. What is the direction of the waves propagation? A. horizontal B. verticle C. diagonal; both horizontal and verticle D. cannot be determined
A the particles within a transverse wave travel in a direction that is perpendicular to the direction of propagation of the wave. If a transverse wave is traveling vertically, the particles in the wave are traveling horizontally.
Which of the following types of waves do not require a medium in order to propagate? A. light B. heat C. transverse, acoustic D. mechanical, longitudinal
A, B and D Sound cannot travel through a vacuum; it requires a medium in order to propagate. Other waveforms such as light; heat and TV waves are capable of traveling through a vacuum
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
Propagation speed can be correctly recorded with which of the following units? A. miles per hour B. mm/sec C. km/sec D. inches per year
A,B,C and D are all correct. Speed is recorded as a distance per unit of time. Any relationship of distance per time is an acceptable answer
The amplitude of an acoustic wave decreases from 27 pascals to 9 pascals. If the initial power in the wave was 27 watts, what is the wave's final power? A. 3 watts B. 9 watts C. 1 watt D. none of the above
A. Alterations in a waves power are proportional to changes in its amplitude squared. The power is reduced to one-third of its previous value (from 27 to 9) one third squared equals one ninth of the waves original power remains. The initial power in the wave was 27 watts, one ninth of that is 27/9 or 3 watts
As an ultrasound wave travels through the body, its amplitude usually: A. decreases B. increases C. remains the same D. cannot be determined
A. As a sound wave travels in the body, its strength or amplitude diminishes. This process is called attenuation. We experience attenuation when walking away from a person who is speaking. The further away we are from a speaker, the weaker that persons voice becomes
Typically, as an ultrasound wave travels through soft tissue, the power of the wave: A. decreases B. increases C. remains the same
A. As a sound wave travels through the body, its power diminishes. This process is called attenuation. Amplitude and power are both measures of strength of an acoustic wave, and tend to decrease as sound travels.
What are the units of the transmitted intensity of a sound wave? A. W/cm squared B. watts C. dB D. none its unitless
A. As sound propagates, one of the ways to measure its strength is to record its intensity.
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.
Sound is best described as _____. A. a series of compressions and rarefactions B. a transverse wave C. a wave humans can hear D. an oblique displacement of acoustic energy
A. Sound is composed of a series of compressions and rarefractions. Molecules in the medium are alternately squeezed together and stretched apart
What happens to an acoustic beams intensity when the power in the beam increases by 25% while the cross-sectional area of the beam remains the same? A. it increases by 25% B. increases by 75% C. it increases by 50% D. decreases by 25%
A. The intensity is equal to the power divided by the beam area. If the power increases by 25% while the beams area is unchanged, then the intensity is also increased by 25%
The speed of sound traveling through bone is ____ soft tissue. A. higher than B. lower than C. equal to D. cannot be determined
A. The propagation speed of sound in bone is higher than in soft tissue. Sound travels at a speed of 3-5km/sec in bone. This is two to three times faster than soft tissue
What determines the period of an ultrasound wave? A. the transducer B. the medium through which the sound travels C. both A and B D. neither choice A nor B
A. The sound source (the transducer) that produces an acoustic signal determines the period of a wave. The waves period is unrelated to the medium through which the sound travels, and will not change as the wave moves from one medium to another.
What is the wavelength of 2 MHz sound in soft tissue? A. 0.77 B cannot be determined C. 1.54 D. 2 mm
A. The wavelength of sound in soft tissue is defined by the following relationship: wavelength (mm) = 1.54 divided by frequency (MHz) 1.54 divided by 2 = 0.77 MHz
The maximum value of the density of an acoustic wave is 60 pounds over inches squared while the minimum density is 20 pounds over inches squared. What is the amplitude of the wave? A. 20 lb/in^2 B. 40 lb/in^2 C. 60 lb/in^2 D. none of the above
A. To calculate the amplitude of a wave, subtract the minimum value of the acoustic variable from its maximum and then divide that number in half. In this case, the maximum minus the minimum is 60-20 = 20 lb/in^2 Half of 40 is 20 lb/in^2
What determines the initial amplitude of an ultrasound wave? A. the transducer B. the medium through which the sound travels C. both A and B D. neither choice A nor B
A. the initial strength or amplitude of a sound wave is determined by the vibration of the piezoelectric crystal in the transducer. The greater the vibration of the crystal, the larger the amplitude of the ultrasound wave.
What determines the initial intensity of an ultrasound beam? A. the source of the sound wave B. the medium through which the sound travels C. both A and B D. neither A nor B
A. the source of acoustic wave determines the initial intensity (as well as the waves amplitude and power) at its point of origin, the strength of an acoustic wave will not be related to the medium that the sound is about to enter.
What establishes the frequency of an ultrasound wave? A. the transducer B. the medium through which the sound travels C. both A and B D. neither choice A nor B
A. when created by a transducer, an ultrasound wave has a specific frequency. The frequency is not determined by the medium through which the sound travels. Only the sound source (the transducer) establishes the waves frequency.
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
As frequency decreases, period ___________________
As frequency decreases, period *increases*
As frequency increases, period ____________________
As frequency increases, period *decreases*
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.
Which of the following is true of all waves? A. they travel through a medium B. all carry energy from one site to another C. their amplitudes do not change D. they travel in a straight line
B Waves carry energy from one site to another. A is incorrect because some waves, such as light, can travel through a vacuum. C is incorrect because many waves get weaker as they travel. Certain waves do not travel in a straight line, so D is also incorrect.
A longitudinal wave propagates from east to west at a speed of 2 miles per hour. what is the direction of motion of the particles within the wave? A. from east to west only B. alternately from east to west and then from west to east C. from north to south only D. alternately from south to north and then north to south
B a longitudinal wave is defined as a wave whose particles vibrate back and fourth in the same direction that the wave is propagating.
The amplitude of an acoustic wave is increased. which of the following will most likely remain unchanged? A. power B. frequency C. period D. intensity
B and C Amplitude relates to the strength of the wave. The frequency of a wave described the number of cycles in one second. A waves period is the time an acoustic variable oscillates though one complete cycle. Frequency and period are not related to amplitude and remain unaltered when the amplitude changes.
In clinical imaging, frequency ranges from approximately ___ MHz to ________ MHz
In clinical imaging, frequency ranges from approximately 2MHz-15MHz
Which of the following are considered acoustic variables? (more than one answer may be correct) A. frequency B. density C. particle motion D. tempature E. period F. pressure
B, C, F and technically D
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
Two sound pulses travel through the same medium. One waves frequency is 2 MHz and the other is 10 MHz. Which sound wave has the longer period? A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined
B. Frequency and period are reciprocals. The wave with a higher frequency has a shorter period. Lower frequencies have longer periods. The 2 MHz wave has a period of 5 times longer than the 10 MHz wave
Two sound pulses travel through the same medium. One waves frequency is 2 MHz and the other is 10 MHz. Which pulse has a longer wavelength? A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined
B. In any specific medium, the wave with the lower frequency has the longer wavelength. The 2 MHz sound's wavelength is five times longer than the 10 MHz wave
What happens when the power in an ultrasound beam is unchanged, and at the same time, the beam area doubles? A.doubles B. is halved C. is quartered D. remains the same
B. Intensity is equal to power divided by beam area. In this case, the power is unchanged while the beams area is doubled. Therefore, the beams intensity is halved.
Which of the following characteristics will create the fastest speed of sound? A. high density, high stiffness B. low density, high stiffness C. high density, low stiffness D. low density, low stiffness
B. Speed is inversely proportional to density and directly proportional to stiffness
Propagation speed is determined by
Medium only - density and stiffness
The propagation speeds of ultrasound waves in muscle, liver, kidney, and blood are ________. A. exactly the same B. very similar to eachother C. vastly different
B. The speed of sound in these media are less than 5% different from each other. The characteristics of muscle, kidney, liver, and blood that determine the wave's speed in the media are quite similar
What is the wavelength of 10 MHz sound in soft tissue? A. 0.77 mm B. 0.15 mm C. 1.54 mm D. 10 mm
B. The wavelength of sound in soft tissue is defined by the following relationship: wavelength = 1.54 divided by the frequency For 2 MHz sound, the wavelength is 1.54 divided by 10 or 0.15 mm
What term describes the number of cycles that an acoustic variable completes in a second? A. period B. frequency C. pulse repetition period D. variable rate
B. This is the definition of the term frequency. Frequency can also be thought of as the number of regularly occurring events in a specific time.
What is the range of periods commonly found in waves produced by ultrasound systems? A. 0.001 to 1 seconds B. 0.06 to 0.5 microseconds C. 0.2 to 1 milliseconds D. 10 to 100 nanoseconds
B. Ultrasonic imaging waves have a period in the range of 0.06 to 0.5 milliseconds. The period is the time of a single cycle. Period is the reciprocal of frequency. A wave with a frequency of 2 MHz has a period of 0.5 milliseconds. A wave with a frequency of 15 MHz has a period of 0.06 milliseconds
The wavelength of a cycle in an ultrasound wave can be reported with which units? A. units of time (sec, min, etc) B. units of distance (feet, etc) C. units of area (meters squared etc) D. mm only
B. Wavelength is the distance from the beginning to the end of one cycle. It has units of distance. In soft tissue, and with frequencies typical of diagnostic imaging, wavelengths range from 0.15 to 0.75 mm. Although it may be impractical to record wavelengths in miles or meters, it can be done since they are distances.
As sound travels through a medium, what term describes the effects of the medium on the sound wave? A. toxic effects B. acoustic propagation properties C. bioeffects D. transmission properties
B. acoustic propagation properties describes the effects of the medium on the wave traveling through it. Acoustic means "sound" propagation means "to travel"
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
What is the wavelength of 2 MHz sound in soft tissue? A. 1.54 mm B. 0.77 mm C. 0.51 mm D. 1.54 km/s E. 3.08 mm
B. in soft tissue, wavelength equals 1.54 mm divided by the frequency in MHz. Thus, 2 MHz sound will have a wavelength of 0.77mm
Infrasound is defined as sound with a frequency of ______. A. greater than 20,000 kHz B. less than 20 Hz C. greater than 10 Mhz D. less than 0.02 MHz
B. infrasound is defined as an acoustic wave with a frequency so low that it is not audiable to humans. Infrasound is an inaudiable wave with a frequency of less than 20 Hz
If intensity remains the same while the power is doubled, what has happened to the beam area? A. quadrupled B. doubled C. halved D. unchanged
B. recall that intensity equals power divided by area. If intensity remains unchanged, then whatever happens to power must also happen to the area. In this case, power has doubled. Therefore, area must have doubled as well
All of the following are true about sound waves EXCEPT: A. they are mechanical B. they are transverse C. they carry energy from place to place D. they generally travel in a straight lube
B. sound waves are not transverse, they are longitudinal
If sound travels at exactly 1,540 m/sec in a particular medium, then the medium ____. A. must be soft tissue B. may be soft tissue C. cannot be soft tissue
B. sound waves travel exactly 1,540 meters per second in soft tissue. however other media have the same propagation speed as that of soft tissue. the medium in question could be something else.
The speed at which a wave travels through a medium is determined by: A. the sound waves properties only B. the mediums properties only C. properties of both wave and medium D. none of the above
B. speed is determined by the characteristics of the medium only. The characteristics of the wave do not affect its speed. All sound waves of any frequency, period, intensity and power travel at the same speed in a particular medium
As sound travels in the body, what happens to the intensity of the wave? A. increases B. decreases C. remains the same
B. the intensity of a sound beam decreases as it travels in the body because of attenuation. Amplitude, Power and Intensity are three different ways to measure the strength of an ultrasound beam, and all decrease as sound propagates.
What is the speed of sound in air? A. 1,540 m/s B. 330 m/s C. 100 m/s D. 3,010 m/s
B. the speed of sound in air is 330 m/s substantially lower than the speed of sound in soft tissue
Compared to soft tissue, the speed of an acoustic wave through lung tissue is ___________________ A. faster B. slower C. equal D. cannot be determined
B. the speed of sound in lung tissue is slower than in soft tissue. Sound travels at speeds in the range of 0.5 to 1.0 km/sec in lung tissue
A pair of waves are in phase. What occurs when these waves interfere? A. reflection B. constructive interference C. refraction D. destructive interference
B. waves that are in phase constructively interfere with each other. The single wave that results from the combination of the two in-phase waves will always have a higher amplitude than either of the original waves.
A sound beam travels a total of 10 cm in 2 seconds. What is the speed of the sound? A. 10 cm/sec B. 2 cm/sec C. 5 cm/sec D. 0.2 cm/sec
C. 10 cm divided by 2 seconds = 5 cm per second
What is the best estimate for the speed of sound in tendon? A. 1,000 m/s B. 1,540 m/s C. 1,754 m/s D. 5,400 m/s
C. Sound travels slightly faster in tendon than in soft tissue
Two waves arrive at the same location and interfere. The resultant sound wave is smaller than either of the two original waves. What is this called? A. constructive interference B. angular interaction C. destructive interference D. in-phase waves
C. Destructive interference results when a pair of out-of-phase waves interfere with each other. The sum of the two out-of-phase waves has a smaller amplitude than at least one of the original waves.
Compare two sound waves, A and B. The frequency of wave A is one third that of wave B. How does the period of wave A compare with the period of wave B? A. A is one-third as long as B B. A is the same as wave B C. A is three times as long as B D. cannot be determined
C. Frequency and period are reciprocals. If the frequency of one wave is one-third as large as another, then the period of the wave will be three times longer than the other.
_______________________ is the reciprocal of period A. inverse period B. pulse repetition period C. frequency D. propagation period
C. Frequency is the reciprocal of period. Reciprocals are related in two ways: - as one increases, the other decreases - when they are multiplied together, the result is unity. For example, a wave with a period of one-hundreth of a second has a frequency of 100 per second or 100 Hz
The frequency of a continuous acoustic wave is 5 MHz. The wave is then pulsed with a duty factor of 0.1. What is the new frequency? A. 0.5 B. 0.5 MHz C. 5 MHz D. 10 MHz
C. Frequency is the reciprocal of the period. the fact that a wave is pulsed rather than continuous does not alter the frequency of the signal. The new and old frequencies are the same, 5 million per second
When a sonographer increases the maximum imaging depth during an exam, what happens to the frequency? A. frequency increases B. frequency decreases C. remains unchanged
C. Imaging depth and frequency are unrelated. When the depth of view is increased, the frequency of sound remains the same.
Which of the following characteristics will create the slowest speed of sound? A. high density, high stiffness B. low density, high stiffness C. high density, low stiffness D. low density, low stiffness
C. Speed is inversely proportional to density and directly proportional to stiffness
The characteristics of four media are described below. Which of the media has the slowest propagation speed? A. high density & high elasticity B. low density and high stiffness C. low stiffness and low density D. low compressibility and low stiffness
C. The compressibility of a medium describes its ability to reduce its volume when a force is applied to it. Elasticity has the same meaning as compressibility. Stiffness describes this same characteristic; however, stiffness is the opposite of compressibility.
The intensity of an ultrasound beam is defined as the __________ in a beam ___________ by the ________________ of the beam A. power, multiplied, diameter B. amplitude, divided, area C. power, divided, area D. amplitude, multiplied, circumfrence
C. The intensity of an ultrasound beam is defined as the *power* in a beam *divided* by the *area* of the beam
What determines the intensity of an ultrasound beam after it has traveled through the body? A. the sound waves source B. the medium through which sound travels C. A and B D. neither A nor B
C. The source and the medium both ultimately determine the residual intensity of an ultrasound beam after it passes through the body
The propagation speed of continuous wave ultrasound is 1.8 kilometers per second. The wave is then pulsed with a duty factor of 50% What is the new propagation speed? A. 0.5 km/sec B. 0.9 km/sec C. 1.8 km/sec D. 3.6 km/sec E. cannot be determined
C. The speed of sound in a medium is determined only by the medium. There is no difference in sounds speed whether the wave is continuous or pulsed. Thus the new and old speeds will be identical, 1.8 km/sec
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
Two sound waves with frequencies of 5 and 3 MHz travel to a depth of 8 cm in a medium and then reflect back to the surface of the body. Which acoustic wave arrives first at the surface of the body? A. the 5 MHz wave B. the 3 MHz wave C. neither D. cannot be determined
C. They both travel at the same speed and reach the surface of the body at exactly the same time. All sound waves, regardless of their features, travel at the same speed in a specific medium. the different frequencies is irrelevent.
If the power in a beam is 1 watt and the area is 5cm squared what is the beams intensity? A. 5 W/cm squared B. 1 W/cm squared C. 0.2 W/cm squared D. 1 watt
C. To answer this question, concentrate on the units. Intensity has units of W/cm squared. Thus, we must find out how many watts there are, and divide them by the number of cm squared. The question states that there is 1 watt. The area is 5 cm squared. Thus the intensity is 1/5 or 0.2W/cm squared
When the elasticity of a medium is high, the ____ is high. A. stiffness B. propagation speed C. compressibility D. reflectivity
C. both elasticity and compressibility describe the ability of a medium to reduce its volume when affected by a force.
With standard ultrasonic imaging, what happens to the period of a wave as it propagates? A. increases B. decreases C. remains the same
C. certain parameters of a wave change as the wave travels through the body. However, the period and the frequency of a wave typically remain constant as a sound wave propagates
What is the wavelength of 3 MHz sound in soft tissue? A. 0.51 m B. 0.51 km C. 0.51 mm D. 0.51 nm E. 0.51 um
C. in soft tissue, wavelength equals 1.54mm divided by the frequency in MHz. Thus, 3 MHz sound will have a wavelength of 0.51mm
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 onle one that has units of time is 0.05 seconds. This must be the answer
Sound can be characterized as: A. energy flowing through a vacuum B. a variable C. cyclical oscillations in certain variables D. a principle of acoustics
C. sound is a wave. a wave is the rhythmical variation throughout time
What is the best estimate of the distance that sound can travel in soft tissue in one second? A. one yard B. one hundred yards C. one mile D. ten miles
C. sound travels at a speed of 1,540 meters per second in soft tissue. This is approximately one mile per second.
If sound doesnt travel at 1,540 m/sec in a medium, then the medium ___ A) must be soft tissue B) may be soft tissue C) cannot be soft tissue
C. sound waves travel exactly 1,540 meters per second in soft tissue. Since the propagation speed of sound in this medium is not 1,540 meters per second then the medium cannot be soft tissue
Waves that exist at the same location and time will combine. What is this called? A. interference B. rarefaction C. interference D. longitudinal interaction
C. the combination of many waves into a single wave is called interference
What term is used to describe the effects of an ultrasound wave on living tissues? A. toxic effects B. acoustic propagation properties C. biological effects D. transmission properties
C. the effects of ultrasound on the tissues are called biological effects or bioeffects. There have been no confirmed bioeffects on humans with acoustic intensities typical of those used in diagnostic imaging.
Two sound pulses travel through the same medium. One waves frequency is 2 MHz and the other is 10 MHz. Which pulse has a lower propagation speed? A. the 10MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined
C. the propagation speeds of all sound waves are identical while traveling in a specific medium
The power of an ultrasound wave can be reported with which of the following units? (more then one answer may be correct) A. watts/square centimeter B. dB/cm C. watts D. kg/cm squared
C. the units of power are watts.
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
What are units of Intensity? A. watts B. watts per centimeter C. watts per centimeter squared D. dB
C. watts per centimeter squared
The wavelength of an ultrasonic wave is determined by: A. the sound source B. the medium through which the wave travels C. both A and B D. neither A nor B
C. wavelength is determined by both the sound source and the medium through which it travels.
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
A sonographer adjusts the output power of the wave emitted by the transducer. Which of the following also changes (more than one answer may be correct) A. pulse repetition period B. PRF C. propagation speed D. intensity
D. As a sonographer adjusts the output power, the intensity will change. The PRF and pulse repetition period will change only when the maximum imaging depth (also called depth of view) changes. The sounds propagation speed will change only if the medium changes.
What is the range of frequencies emitted by transducers used in ultrasonic imaging? A. 1-3MHz B. 1-1,000 kHz C. -10,000 to +10,000 Hz D. 2,000,000 to 15,000,000 Hz
D. Frequencies commonly used in diagnostic imaging range from approximately 2-15 MHz or 2-15 million cycles per second
When the power in an acoustic beam is doubled and the cross-sectional area of the beam is halved, then the intensity of the beam is: A. doubled B. halved C. quartered D. four times larger
D. The intensity rises to four times its original value. Intensity is equal to power divided by beam area. In this case, the power is doubled and the area is halved.
Ultrasound is defined as a sound with a frequency of _______. A. greater than 2,000 kHz B. less than 1 kHz C. greater than 10MHz D. greater than 0.02 MHz
D. Ultrasound is defined as an acoustic wave with a frequency so high that it is not audible to humans. Ultrasound is an inaudiable wave with a frequency of at least 20,000Hz, 20 kHz, or 0.02 MHz
The direction o motion of a particle in a wave is perpendicular to the direction of propagation of the wave. What type of wave is this? A. longitudinal B. acoustic C. mechanical D. transverse
D. a characteristic of transverse waves is that the direction of propagation is perpendicular to the direction of particle motion in the wave. Sound waves are not transverse, but rather longitudinal
What is the propagation speed of a 5 megahertz sound wave in soft tissue? A. 1,450 m/s B. 1,540 km/sec C. 1.54 m/s D. 1.54 mm/us
D. any speed of any sound wave moving through soft tissue, regardless of frequency, is 1,54 mm/us, 1,540 m/s, or 1.54 km/s
The final amplitude of an acoustic wave is reduced to one-half of its original value. The final power is ________ the original power A. the same as B. one-half C. double D. none of the above
D. changes in the power of a wave are proportional to changed in the wave's amplitude squared. one half squared equals one quarter (1/2 x 1/2 = 1/4) When one half of the waves
As a general rule, which of the following lists media in increasing order of propagation speeds? A. gas, solid, liquid B. liquid, solid, gas C. solid, liquid, gas D. gas, liquid, solid
D. generally, sound travels slowest in gases, faster in liquids and fastest in solids
Which of the following describes the characteristics of a sound wave? A. longitudinal, non mechanical B. mechanical, transverse C. transverse, acoustic D. mechanical, longitudinal
D. sound is a mechanical, longitudinals wave.
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
Two sound pulses travel through the same medium. One waves frequency is 2 MHz and the other is 10 MHz. Which pulse has the lowest power? A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined
D. the power of a wave is not related to its frequency. The power relates to the strength of a wave, and in this case, no information is provided about the power. therefore we cannot answer the question based on the information provided
Which of the following terms best describes the relationship between frequency and wavelength for sound traveling in soft tissue? A. reciprocal B. direct C. related D. inverse
D. the relationship between frequency and wavelength is inverse. Higher frequency waves are related to shorter wavelengths. Lower frequency waves are related to longer wavelengths.
Two sound pulses travel through the same medium. One waves frequency is 2 MHz and the other is 10 MHz. Which pulse has a longer spatial pulse length? A. the 10 MHz wave B. the 2 MHz wave C. neither wave D. cannot be determined
D. the spatial pulse length is equal to the wavelength multiplied by the number of cycles in the pulse. The number of cycles that comprise each pulse is unknown.
What two properties establish sounds propagation speed in a given medium? A. elasticity and stiffness B. stiffness and impedence C. conductance and density D. density and stiffness
D. the two properties of the medium that affect sounds propagation speed are density and stiffness
What is characteristic of acoustic waves with frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000Hz? A. they travel more effectively in soft tissue B. they travel more rapidly C. they attenuate less when traveling D. humans cant hear them
D. waves with frequencies exceeding 20kHz are inaudiable to humans and are called ultrasonic. They travel at the same speed as waves with lower frequencies and attenuate at a faster rate than waves with lower frequencies
What is characteristic of acoustic waves with frequencies of less than 20 Hz when compared with waves having frequencies of more than 20 Hz? A. they travel less effectively in soft tissue B. they travel more rapidly C. they attenuate more when traveling in soft tissue D. humans cant hear them
D. waves with frequencies of less than 20 Hz are inaudiable to humans and are called infrasonic. They travel at the same speed as waves with higher frequencies and attenuate at a lesser rate than waves at higher frequencies
What is the wavelength of a wave with an unknown frequency traveling in soft tissue? A. 0.51 us B. 0.51 m/s C. 0.51 pascals D. 0.51 watts E. 0.51 mm
E. is the only answer with units of distance. A is units of time B is units of speed C is units of pressure and D is units of power The only possible choice is E
Which of the following cannot be considered a unit of frequency? A. per day B. cycles per second C. Hz D. Hertz E. cycles
E. the term cycles informs us of the number of events but does not inform us of the duration of time required for those events to occur.
True or False. If the power of a wave is halved, the intensity is reduced to one-fourth its original value
False. Intensity is the power of a beam divided by its cross-sectional area. If we halve the power, we ill halve the intensity
True or False. Propagation speed increases as frequency increases.
False. Propagation speed is determined by the medium only. frequency and speed are unrelated
True or False. Propagation speed increases as frequency decreases.
False. Speed and frequency are unrelated
True or False. Propagation speed increases as frequency increases.
False. Speed and frequency are unrelated
True or False? The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer.
False. The sonographer cannot adjust the period (or frequency) of a wave produced by a basic transducer. Think of striking a key on a piano. The frequency of sound created by striking a single key is constant
Intensity formula:
I (W/cm^2) = P (w) /A (cm^2)
Medium 1 has a density of 9 and a stiffness of 6. Medium 2 has a density of 8 and a stiffness of 6. In which medium will sound travel slower?
Medium 1. Since both media have the same stiffness, the medium with the greater density has the lower propagation speed.
The effects of sound waves on tissue in the body are called ________________________
The effects of sound waves on tissue in the body are called *bioeffects*
Mathematically, when a number is squared, the number is multiplied by: A. 2 B. 0.5 C. itself D. 1.5
To square a number means to multiply the number by itself. Hence, the term "five squared" means 5 times 5 or 25. Ten squared is 10 times 10 or 100
True or False? with diagnostic ultrasonic imaging instruments, the operator can alter the intensity of an ultrasound beam produced by a transducer.
True. Although operators cannot change all the characteristics of an ultrasound beam produced by an individual transducer, they can change the initial power. As the operator increases the output power of a transducer, the initial intensity increases.
True or False? If the periods of two waves are the same, then the frequencies of the waves must also be the same.
True. Frequency and period are reciprocals. When the periods of two waves are identical, the frequencies of the waves must also be identical
True or False. Propagation speed does not change as frequency increases
True. Propagation and frequency are unrelated
True or False? Soft tissue is an imaginary construct that actually does not exist.
True. Soft tissue is an imaginary structure with characteristics that represent an "average" of body tissues, including muscle, blood, kidney, and spleen. It is used as an approximation
True or False? The period of an ultrasound wave is related to the frequency and is the same, regardless of whether the wave is pulsed or continous
True. The period of a wave is characteristic of each individual cycle in the wave. The period of a wave (as well as frequency and wavelength) remains unchanged, whether the wave is continuous or pulsed
True or False? Waves in the ultrasound range behave in the same general manner as sound waves that are audiable
True. The primary difference between audiable and ultrasonic waves is that humans can hear is that humans can hear audiable waves. A waves behavior or adherence to physical laws and principles is generally the same, regardless of whether it can be heard by humans.
True or False? With standard diagnostic imaging instrumentation, the sonographer has the ability to vary the amplitude of a sound wave produced by the transducer.
True. The sonographer can adjust the strength of the ultrasound signal that a transducer creates. When a sonographer increases the output power, the electrical voltage sent to the transducer is increased. This produces a more violent vibration of the piezoelectric crystal within the transducer and, in turn, a stronger ultrasound wave.
True or False. A wave with a frequency of 15,000 MHz is ultrasonic
True. Ultrasound is defined as any wave with a frequency greater than 20,000 hertz. 15,000 MHz is a frequency of 15,000,000,000 hertz
True or False? Shorter wavelength sound creates higher quality images with greater detail
True. Wavelength plays a very important role in image quality. Shorter wavelength (higher frequency) produces higher quality images with greater detail.
Typical values for Power range from _______ to ________ milliwatts
Typical values for power range from 4-9 milliwatts
What are the units for power?
Watts (W)
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
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
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
The power of a beam is tripled while the cross-sectional area of the beam remains the same, the intensity __________ A. triples B. increases nine fold C. remains the same D. none of the above
When the cross-sectional area of a beam remains unchanged, the change in the intensity of a beam is proportional to the change in the power. If power is tripled, then the intensity is also tripled.
When you think of Power, it helps to think of a _______________ ______________
When you think of power it helps to think of a *light bulb*
Stiffness and speed are ______ related.
directly; when Stiffness increases, Speed increases
If a waves power is doubled, intensity is _______.
doubled
What are the units for wavelength?
meters (m) or millimeters (mm) or any other unit o length
Period is determined by: Can it be changed?
period is determined by the ~sound source ~ & Cannot be changed
Intensity is ____________________ to power
proportional
Amplitude is determines by:
the sound source
