CHP 6 Review Questions: Interaction of Sound and Media

202. A sound wave reaches a rough or irregular border between two media. Under these explicit circumstances, which process is most likely to occur? A. backscatter reflection B. specular reflection C. Rayleigh scattering D. refraction

A. The smoothness or roughness of a boundary will help to determine what form of reflection takes place. Backscatter is likely to occur when the boundary has irregularities that are larger than the wavelength of the incident acoustic pulse. Diffuse reflection is another name for backscatter. Ch. 6 Pg. 82

211. Ultrasound waves traveling through lung tissue attenuate to a ____ extent than when traveling through soft tissue. A. greater B. lesser C. nearly equal

A. Ultrasound attenuates more when traveling through lung tissue than when traveling through soft tissue. Ch. 6 Pg. 86

187. Which of the following reports the relative strength of an ultrasound wave? A. decibels B. watts C. W/cm^2 D. pascals

A. decibels (The relative strength of a sound beam may be reported in decibels. The term "relative" indicates a comparison between two values, such as a beam has decreased in strength by 50%.) Ch. 6 Pg. 77

227. A wave strikes an interface between two media and intensities are measured at the interface. What results when the reflected intensity is divided by the incident intensity? A. intensity reflection coefficient B. intensity transmission coefficient C. beam uniformity coefficient D. none of the above

A. intensity reflection coefficient (Intensity reflection coefficient is the percentage of the incident intensity that is reflected as a wave strike a boundary between two media.) Ch. 6 Pg. 93

226. What are the units of the intensity reflection coefficient? A. none B. W/cm^2 C. watts D. dB

A. none Ch. 6 Pg. 93

189. What is the decibel representation when an acoustic signal is amplified? A. positive B. negative C. equal to zero

A. positive (When a signal is amplified, its magnitude increases and becomes stronger. In decibel notation, an increase in signal strength is described with positive decibels.) Ch. 6 Pg. 78

196. What does a 3 dB change in a value intensity mean? A. the value has doubled B. the value has tripled C. the value has increased 30% D. the value has increased ten times

A. the value has doubled (A 3 decibel change in the intensity indicates that the value has doubled.) Ch. 6 Pg. 78

3. If the media are soft tissue, what is an estimate of the ultrasound frequency?

About 7 MHz; the attenuation coefficient multiplied by 2 approximates the frequency (3.5 x 2 = 7). Ch. 6 Pg. 85

9. What processes occur as the ultrasound passes through all media? What are the units of this process?

Attenuation (scattering, absorption, and reflection). Units: dB. Ch. 6 Pg. 103

193. How many decibels represent a 100-fold increase in the intensity of an acoustic pulse? A. 10 B. 20 C. 100 D. 6

B. 100 (An increase of 100 times the intensity of a wave is equal to 20 dB. Each 10 dB indicates a tenfold increase. Therefore, 20 indicates (two 10 increases) means a pair of tenfold increases, 10 x 10 = 100.) Ch. 6 Pg. 78

3. A reduction in the intensity is a sound beam to one-half of its original value is ____ dB.

-3dB Ch. 6 Pg. 78

3. A reduction in the intensity of a sound beam to one-quarter of its original value is ____ dB.

-6dB Ch. 6 Pg. 78

6. dB is a mathematical representation with a _____ and _____ scale. a. logarithm and relative b. division and relative c. longitudinal and relative d. logarithmic and absolute

A logarithmic and relative Ch. 6 Pg. 77

1. Sound is traveling from bone to soft tissue. The impednaces of the media differ significantly, and 90% of the beam's intensity is reflected. What percentage of the intensity is transmitted?

10% must be transmitted Ch. 6 Pg. 97

2. Sound is traveling in a medium and strikes a boundary with normal incidence. If 63% of the wave's intensity is reflected back toward the transducer, what percentage is transmitted?

37% of the intensity will be transmitted. The sum of the reflected and transmitted intensities must equal 100%. 63% + 34% = 100% Ch. 6 Pg. 94

1. A pulse of ultrasound is propagating in soft tissue, such as liver. The pulse strikes a boundary with a different tissue at normal incidence. What portion of the intensity is reflected back toward the transducer? Why?

A very small percentage of sound, typically less that 1%, is reflected at a boundary between two soft tissues. The impedances of two soft tissues are similar, and the difference in impedance directly determines the intensity reflection coefficient. Very little reflection occurs when the impedances have similar, but not identical values. Ch. 6 Pg. 95

2. A sound wave with an intensity of 50 W/cm^2 strikes a boundary and is totally reflected. What is the reflected intensity? A. 50 w/cm^2 B. 25 w/cm^2 C. 0 w/cm^2 D. 100% E 0

A. Since the wave is totally reflected, intensity is 50 w/cm^2 Ch. 6 Pg. 94

210. The attenuation of an acoustic wave traveling through bone is ____ its attenuation through soft tissue. A. greater than B. less than C. equal to

A. The attenuation of ultrasound in bone is greater than its attenuation in soft tissue. Ch. 6 Pg. 86

217. Which two ATTRIBUTES help establish the acoustic impedance of a medium? a. density and temp b. density and stiffness c. stiffness and eslastance d. elasticity and compressability

B. Density and stiffness To calculate the acoustic impedance multiply the propagation speed of the medium by the density of the medium. A mediums propagation speed is determined by the density and the stiffness of the medium therefore the acoustic impedance is a property of both density and stiffness. Ch. 6 Pg. 88

5. Which of the following terms does not belong with the others? A. orthogonal B. oblique C. normal D. perpedicular

B. Oblique Ch. 6 Pg. 95

3. A sound pulse travels in Medium 1 and strikes an interface with another tissue, Medium 2, at 30 degrees. The angle of transmission is 10 degrees. In which medium does sound travel slowest? A. Medium 1 B. Medium 2 C. cannot be determined.

B. Sound travels slowest in medium 2. When the angle of transmission is less than the angle of incidence. sound travels slower in the second medium. Ch. 6 Pg. 104

208. What is the amount of attenuation per centimeter that a sound wave undergoes called? A. beam uniformity coefficient B. AC C. attenuation D. DF

B. The AC reports a sound beam's decibels of attenuation per centimeter. This is a useful tool as its value remains constant, regardless of actual path length. Ch. 6 Pg. 84

207. As a pulse passes through soft tissue, a certain amount of acoustic energy remains in the tissue as heat. What is this constituent of attenuation called? A. scattering B. absorption C. refraction D. rarefaction

B. The conversion of acoustic energy into heat is called absorption. This process deposits a portion of energy from the beam into the soft tissues. Ch. 6 Pg. 84

212. Sound traveling through blood attenuates to a ____ extent than when traveling through soft tissue. A. greater B. lesser C. relatively equal

B. Ultrasound waves attenuate less when traveling through blood than when traveling through soft tissue. Ch. 6 Pg. 86

219. What of the following describes an angle with a measure of 45 degrees? A. orthogonal B. acute C. obtuse D. normal

B. acute Ch. 6 Pg. 90

229. An ultrasound wave strikes an interface between two media. All intensities are measured directly at the interface. What results when the transmitted intensity is divided by the incident intensity? A. intensity reflection coefficient B. intensity transmission coefficient C. beam uniformity coefficient D. none of the above

B. intensity transmission coefficient (Intensity transmission coefficient is the percentage of incident intensity that continuous to propagate in the forward direction when the incident wave strikes a boundary between two media.) Ch. 6 Pg. 93

190. What is the decibel notation for an acoustic signal that is attenuated? A. positive B. negative C. equal to zero

B. negative (When a signal is attenuated, its magnitude decreases and it becomes weaker. In decibel notation, a decrease in signal strength is described with negative decibels.) Ch. 6 Pg. 78

216. To calculate the acoustic impedance of a medium, one should ____________ the ____________ by the _____________. a. /, ps, density b. *, density, ps c./, density, ps d. *,stiffness, density

B. to attain the value of acoustic impedance multiply the density of a medium by its prop speed. Ch. 6 Pg. 88

5. The incidence between the sound wave and the boundary between Media 1 and 2 is normal. What happens at the boundary between Media 1 and 2? Why?

Both reflection and transmission occur. There are normal incidence and different acoustic impedances. Ch. 6 Pg. 91

8. A wave's intensity is 2 mW/cm ^2. There is a change of +9 dB. What is the final intensity? A. 6 mW/cm^3 B. 2 mW/cm^2 C. 16 mW/cm^2 D. 16 uW/cm^2

C 16 mW/cm^2 Ch. 6 Pg. 78

232. What is the maximum permissible value for both the intensity reflection coefficient and the intensity transmission coefficient? A. 100 B. 1% C. 1 D. infinity

C. 1.0 (The max percentage of the incident intensity that either reflects or transmits is 1.0 or 100%. At the extremes, total reflection occurs or complete transmission occurs. The upper limit of both of these coefficients is 1.0.) Ch. 6 Pg. 97

192. The power in a wave is increased to ten times its original value. How many decibels describe this change? A. 3 B. 6 C. 10 D. 20

C. 10 (An increase of ten times the original power of a wave is reported as +10 dB.) Ch. 6 Pg. 78

234. A sound beam with an intensity of 45 W/cm^2 strikes a boundary and 70% of the waves intensity is reflected. How much is transmitted? A. 45 W/cm^2 B. 25 W/cm^2 C. 30% D. 100%

C. 30% (100% - 70% = 30%) Ch. 6 Pg. 94

197. As sound propagates through a medium, the total power in the wave decreases. What is this entire process called? A. absorption B. scattering C. attenuation D. reflection

C. As a wave propagates through a medium, its power diminishes. This is attenuation. Choices A, B, and D are all components or contributors to attenuation. Ch. 6 Pg. 80

203. Which of the following is true of diffuse reflections? A. they're created by smooth boundaries B. they're created by large reflectors C. sound reflects in many directions D. they do not appear in soft tissue

C. Diffuse reflections, also called backscatter, are dispersed in multiple directions. Ch. 6 Pg. 82

200. Which of the following is not one of the physical processes that contributes to attenuation of ultrasound waves passing through soft tissue? A. reflection B. redirection of sound in many directions C. focusing D. conversion of acoustic energy to heat

C. Focusing does not contribute to the attenuation process. In contrast, choices A, B, and D reduce the intensity of a wave as it propagates. Ch. 6 Pg. 80

204. What is the uniform dispersion of a sound wave in many different directions after striking a very small particle? A. microscattering B. backscattering C. Rayleigh scattering D. total absorption

C. Rayleigh scattering is the redirection of an acoustic wave in many different directions as a result of striking a small particle. When Rayleigh scattering occurs, the dimension of the reflecting particle is usually less than the wavelength of the ultrasound wave. The amount of Rayleigh scattering also depends on the frequency of the ultrasound. Ch. 6 Pg. 83

201. An acoustic pulse reflects from a very smooth boundary where the irregularities on the surface of the boundary are much smaller than the pulse's wavelength. What type of reflection is most likely to occur under these circumstances? A. partial B. Rayleigh C. specular D. total

C. Reflections from a smooth boundary are specular. A mirror is a specular reflector. The waves strike this smooth boundary and reflect in an organized, systematic manner. A boundary is considered smooth when irregularities in its surface are smaller than the wavelength of the incident ultrasonic beam. Ch. 6 Pg. 81

4. A sound pulse travels in medium 1 and strikes an interface with another tissue, medium 2, at 30 degrees. The angle of transmission is 10 degrees. In which mediums is the impedance higher? A. Medium 1 B Medium 2 C. cannot be determined

C. Refraction of sound at a boundary is unrelated to the impedances of the media. Therefore, with the information provided, it cannot be determined which material has the greater impedance. Refraction is affected by the speed of sound in media. Ch. 6 Pg. 104

206. To which of the following is Rayleigh scattering related? A. half of the wavelength B. square root of propagation speed C. frequency^4 D. PRF^2

C. The degree to which a wave exhibits Rayleigh scattering is related to frequency raised to the fourth power. That is, if the frequency is twice as high, Rayleigh scattering is increased 16-fold: 2^4 = 2 x 2 x 2 x 2 = 16. Ch. 6 Pg. 83

199. An acoustic wave is traveling through soft tissue. Its intensity undergoes six decibels of attenuation. How does the final intensity of the wave relate to the intensity of the wave when it started on its journey? A. it is now 4x larger B. it is now 6x larger C. it is not 1/4 as large D. it is now 1/10 as large

C. When a wave undergoes 6 dB of attenuation, the intensity of the wave is decreased to 1/4 of its initial value. The term attenuation means "to weaken, or reduce." Attenuation always describes a reduction in the intensity of the wave. Six decibels of attenuation is made up of two groups of -3 dB. Each -3 dB indicates a halving of intensity. 1/2 multiplied by 1/2 means that only 1/4 of the original intensity remains. Ch. 6 Pg. 80

185. What is a decibel? A. the absolute value of a number B. a range of values C. a relationship between two numbers D. none of the above

C. a relationship between two numbers (A decibel represents a relationship between two numbers. A decibel is a relative measure of intensity or power. The term "relative" indicates that we are not dealing with an absolute power, but rather with how the power is related to a reference level.) Ch. 6 Pg. 77

235. If the ___ of two media are different and sound strikes a border between the media at 90 degree incidence, then reflection will occur. A. conductances B. densities C. impedances D. propagation speeds

C. impedances (Under the conditions of orthogonal or normal incidence, reflection depends on differences in the acoustic impedances of the media on either side of the boundary. With normal incidence, as long as the impedances are dissimilar, reflection will always occur.) Ch. 6 Pg. 95

188. The scale associated with decibel notation is ___? A. linear B. discrete C. logarithmic D. additive

C. logarithmic Ch. 6 Pg. 76

222. Which term does not belong in the group below? A. orthogonal B. at right angles C. oblique D. 90 degrees E. normal F. perpendicular

C. oblique Ch. 6 Pg. 90

224. Which term has a meaning other than normal incidence? A. orthogonal incidence B. perpendicular incidence C. oblique incidence

C. oblique incidence Ch. 6 Pg. 91

220. Which of the following describes an angle with a measure of 123 degrees? A. orthogonal B. acute C. obtuse D. normal

C. obtuse Ch. 6 Pg. 90

194. The intensity of an ultrasound wave is changes by -6 dB. This means that a current intensity is ___ as much as its original level. A. one-tenth B. four times C. one-forth D. one-sixth

C. one-forth (A change in intensity of -6 dB indicates that only one-forth of the initial intensity remains. The minus sign indicates a decrease in signal magnitude. Each -3 dB change means that one-half of the original intensity remains. Since there are two sets of -3 dB, one-half multiplied by one-half indicates that there is only one-forth remaining.) Ch. 6 Pg. 78

6. A sound wave strikes a boundary with normal incidence. The impedances of the two media are identical. What percentage of the sound wave is refracted? A. 100% B. 75% C. 0% D. 25% E. 90%

C. remember, refraction cannot occur with normal incidence. Ch. 6 Pg. 104

191. The intensity of a signal declines from 1.5 mW/cm^2 to 0.75 mW/cm^2. How many decibels is this change in intensity? A. 3 dB B. 0.75 dB C. -0.75 dB D. -3 dB

D. -3 dB (A decline in intensity to one-half of the original level is a change of -3 dB. When the new level is less than the reference level, the reported decibels must be negative. When the new intensity is greater than the reference level, the change in decibels is positive.) Ch. 6 Pg. 78

233. What is the minimum permissible value for both the intensity reflection coefficient and the intensity transmission coefficient? A. different from each other B. -1 C. 100% D. 0

D. 0 (The minimum value for the intensity transmission and the intensity reflection coefficient is zero. At one extreme, it is possible to have total transmission and no reflection. At the other extreme, it is possible for total reflection to occur. No transmission would exist and the intensity transmission coefficient = 0.) Ch. 6 Pg. 97

230. What results when the intensity transmission coefficient are added together? A. incident intensity coefficient B. acoustic impedance C. total intensity D. 1.0

D. 1.0 (The sum of the IRC and the ITC equals one or 100%. The ITC is the percentage of a sound wave's intensity that is reflected at a boundary. Since there is conservation of energy at the boundary, these percentages added together equal 100% or 1.0.) Ch. 6 Pg. 94

184. The logarithm of a numeral is defined as how many times ___ must be multiplied together to get that numeral. A. 1 B. 2 C. 5 D. 10

D. 10 (The logarithm of a numeral is equal to the number of tens that are multiplied together to result in the number.) Ch. 6 Pg. 76

2. Sound that is traveling in Jell-O passes through an interface at 90 degrees and continues to travel in whipped cream. The impedance of Jell-O and whipped cream are nearly identical. What percentage of the intensity is transmitted? A. 2% B. 25% C. 78% D. 99%

D. 99%. The the impedance of Jell-O and whipped cream are nearly identical, only a very small percentage of the beam's intensity will reflect. The remainder will transmit. Ch. 6 Pg. 97

205. Which of the following is considered a Rayleigh scatterer? A. bone B. liver C. muscle D. blood cell

D. A blood cell is a Rayleigh scatterer. A red blood cell is smaller than the wavelength of the typical acoustic wave used in diagnostic imaging. When an acoustic wave strikes a blood cell, the energy within the pulse is scattered in many directions. Ch. 6 Pg. 83

1. A sound wave with an intensity of 50 W/cm^2 strikes a boundary and is totally reflected. What is the intensity reflection coefficient? A. 50 w/cm^2 B. 25 w/cm^2 C. 0 w/cm^2 D. 100% E. 0

D. Since the wave is totally reflected, the intensity reflection coefficient is 100%. Ch. 6 Pg. 94

198. Attenuation is determined by which of the following factors? A. density and stiffness of the medium B. frequency of sound and propagation speed C. PRF of sound and path length D. path length and frequency of sound

D. The factors that determine the degree to which a sound beam weakens are: 1. the distance that the sound travels 2. the frequency of the sound Ch. 6 Pg. 80

213. Which of these lists indicates media with increasing attenuation of ultrasound? A. water, lung, soft tissue, bone, air B. lung, air, soft tissue, bone C. lung, fat muscle D. water, blood, fat, muscle, bone, air

D. This list orders tissues with increasing attenuation rates of ultrasound. Ch. 6 Pg. 86

195. What units are used to describe attenuation? A. watts B. watts/cm2 C. macro D. decibels

D. decibels Ch. 6 Pg. 80

228. An ultrasound wave strikes a boundary between two media. All intensities are measured directly at the boundary. What results whens the transmitted intensity is divided by the reflected intensity? A. intensity reflection coefficient B. intensity transmission coefficient C. beam uniformity coefficient D. none of the above

D. none of the above Ch. 6 Pg. 93

225. What are the units of the intensity transmission coefficient? A. watts/square cm B. watts C. dB D. none of the above

D. none of the above (Intensity transmission coefficient is defined as the percentage of an ultrasound beam's intensity that is transmitted as the sound wave passes through a boundary between two media.) Ch. 6 Pg. 93

223. A sound wave strikes a boundary between two media at a 60 degree angle. This is called a ___ incidence. A. orthogonal B. angular C. obtuse D. oblique

D. oblique Ch. 6 Pg. 90

221. The angle between the direction of propagation and the boundary between two media is 90 degrees. What term describes the form of incidence of the wave? A. not normal B. direct C. oblique D. orthogonal

D. orthogonal Ch. 6 Pg. 91

186. Decibel notation is a ___ between two numbers. A. difference B. sum C. product D. ratio

D. ratio (Decibels are calculated by dividing the final strength of a signal by the starting strength. Thus, decibel notation is a ratio between two numbers.) Ch. 6 Pg. 77

231. What remains when the reflected intensity is subtracted from the incident intensity? A. 1.0 B. incident intensity C. transmitted intensity coefficient D. transmitted intensity

D. transmitted intensity (At any point in time and space, there must be a conservation of energy. In other words, all energy must be accounted for. The intensity of a wave as it reaches a border between two media is called incident intensity as it strikes the boundary, redirected toward the sound source. This is called the reflected intensity. The remainder of the energy continues to propagate and is called the transmitted intensity.) Ch. 6 Pg. 97

1. Every 3 dB change means that the intensity will ________.

Double Ch. 6 Pg. 78

7. True or false. We need one intensity to calculate decibels.

False Ch. 6 Pg. 76

4. What property has units of rayls? How is it determined?

Impedance is calculated , not measured. Impedance = density x speed. Ch. 6 Pg. 88

8. What is the relationship between ultrasound frequency and the attenuation coefficient in soft tissue?

In soft tissue, the attenuation coefficient in dB per centimeter is approximately one half of the ultrasonic frequency in MHz. Ch. 6 Pg. 87

2. Every 10 dB change means the intensity will _______.

Increase 10 times Ch. 6 Pg. 78

2. As the path length increases, the attenuation of ultrasound in soft tissue _____.

Increases Ch. 6 Pg. 80

15. Two media A and B have the same densities. The speed of sound in medium A is 10% higher than in medium B. Which medium has the higher acoustic impedance?

Medium's A acoustic impedance is higher than medium B's. Recall that impedance equals speed multiplied by density. Since both media have identical densities and mediums A's speed is 10% higher, then medium A's impedance is 10% higher. Ch. 6 Pg. 88

7. What type of incidence is there between Media 3 and 4?

Oblique. Ch. 6 Pg. 103

4. -10 dB means the intensity is reduced to _____ of its original value.

One-tenth Ch. 6 Pg. 78

10. If the initial intensity of a sound beam is less than the final intensity, then the gain in dB is _____ (+ or -).

Positive. The beam's intensity is increasing. Ch. 6 Pg. 78

9. If the final intensity of a sound beam is more than the initial intensity, then the gain in dB is _____ (+ or -).

Positive. The beam's intensity is increasing. Ch. 6 Pg. 78

8. What happens at the boundary between Media 3 and 4? Why?

Reflection may occur. If transmission does occur, the sound beam will refract because there are different propagation speeds and oblique incidence. Ch. 6 Pg. 103

214. T/F: Attenuation and propagation speed are unrelated.

TRUE. Attenuation and propagation are entirely unrelated. Attenuation is the WEAKENING of a beam as it travels and has nothing to do with how FAST it travels. Ch. 6 Pg. 87

2. What does the 3.5 dB/cm represent?

The attenuation coefficient of the sound in the media. Ch. 6 Pg. 84

17. Which is better to use while examining a carotid artery, a 7.5 or 3.0 MHz transducer?

The carotid artery is a superficial structure. A 7.5 MHz transducer is better because the higher frequency transducer produces the better image. Ch. 6 Pg. 87

1. What does the 100 mW/cm^2 represent?

The incident intensity of the sound beam. Ch. 6 Pg. 92

209. A sound beam travels 9 cm in soft tissue. The AC is 3 dB/cm. What is the total attenuation that the beam experienced? A. 9 dB B. 3 dB C. 27 dB D. 18 dB

To calculate total attenuation, multiply path length by AC. In this example, the overall attenuation is 3 x 9 = 27 dB. Ch. 6 Pg. 85

6. The incidence between the sound wave and the boundary between Media 2 and 3 is normal. What happens at the boundary between Media 2 and 3? Why?

Transmission only. The impedances of the media are the same. Ch. 6 Pg. 91

7. True or False. In a given medium, attenuation is unrelated to the speed of sound.

True. Attenuation and propagation speed are unrelated. Ch. 6 Pg. 80

3. Sound strikes a boundary between two medial orthogonally. Although the media are very different, no reflection is created. How can this be?

With normal impedance, reflections occur only when the impedances of the two medial at the interface are different. Two different medial can have the same impedances, ill be and when that happens, no reflection will be created. Ch. 6 Pg. 95

5. Sound travels in a medium and orthogonally strikes a boundary with a different medium. Although sound waves traveling in the media have vastly different speeds, there is no refraction. How can this be?

With normal incidence, refraction cannot occur. Refraction occurs only when there are different speeds and oblique incidence. Both conditions must be met. In this example, the incidence is normal, no refraction can occur. Ch. 6 Pg. 104

1. Name the three components of attenuation.

absorption, scattering, and reflection Ch. 6 Pg. 81

215. Acoustic impedance is a property of _____________ and has units of ______________. a. source of medium lmps b. medium, dB c. medium, rhayls d. medium ohms

c. Medium and rhayls Acoustic impedance is a property of the medium through which sound travels. It is UNEFFECTED BY SOUND SOURCE or characteristic of the wave itself Units of impedence are Rhayls Ch. 6 Pg. 88

217. Which is the closest to the impedance of soft tissue? A. 1.5 kRayls B. 2.5 deci Rayls C. 19 megaRayls D. 2,mill rayls

d. 2 million Rayls choices a and b are far too low and choice C is too high. The impedance of soft tissue is in the range of 1.5-2.5 ,million rayls. Ch. 6 Pg. 88

6. What are the units of attenuation?

dB (decibels) Ch. 6 Pg. 80

9. What are the units of half-value layer thickness?

distance: centimeters Ch. 6 Pg. 87

3. Attenuation in lung tissue is [less than, greater than, the same as] attenuation in soft tissue?

greater than Ch. 6 Pg. 86

4. Attenuation in bone is _____ attenuation in soft tissue.

greater than Ch. 6 Pg. 86

5. Attenuation in air is _____ attenuation in soft tissue.

greater than Ch. 6 Pg. 86

14. Acoustic impedance = ______ X _____.

impedance = density (kg/m^3 X propagation speed (m/s) Ch. 6 Pg. 88

10. As frequency decreases, depth of penetration _____.

increases Ch. 6 Pg. 87

12. Impedance is associated with _____.

only with the medium Ch. 6 Pg. 88

16. Impedance is important in _____ at boundaries.

reflections Ch. 6 Pg. 88

11. As path length increases, the half boundary layer _____.

remains the same Ch. 6 Pg. 87

13. As the path length increases, the attenuation coefficient of ultrasound in soft tissue [decreases, remains the same, increases].

remains the same Ch. 6 Pg. 87