Intensities
Logarithms and Decibels
Attenuation, Reflection, and Scattering
Impedance and Incidence
Reflection and Transmission
100

With a continous wave sound beam, which of the following 4 intensities are the same?

1. SPTA

2. SAPA

3. SATA

4. Im

2 & 3 (SAPA and SATA)
100

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
100

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. attenuation
100

Which of the following describes an angle with a measure of 45 degrees?

a. orthogonal

b. acute

c. obtuse

d. normal

b. any angle with a measure less than 90 degrees is an acute angle
100

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
200

The SPTP intensity of a typical pulsed acoustic wave ____.

a. Exceeds the SATA intensity

b. Exceeds the SPTA intensity

c. Exceeds the SATP intensity

d. All of the above

d. All of the above
200

dB is a mathematical representation with a ____ scale.

a. Logarithmic and relative

b. Division and relative

c. Longitudinal and relative

d. Logarithmic and absolute

a. Logarithmic and relative
200

Which of the following is true of diffuse reflection?

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. sound reflects in many directions
200

Acoustic impedance is a property of the ___ and has units of ____.

a. source and medium, lmps

b. medium, dB

c. medium, Rayls

d. medium, Ohms

c. medium, Rayls
200

What results when the intensity transmission coefficient and the intensity reflection coefficient are added together?

a. incidence intensity coefficient

b. acoustic impedance

c. total intensity

d. 1.0

d. 1.0

IRC + ITC = 1 or 100%

300

What does the beam uniformity coefficient (also called SP/SA factor) measure?

a. Special distribution of sound energy

b. Spatial distribution of acoustic energy

c. Temporal distribution of sound energy

d. None of the above

b. Spatial distribution of acoustic energy
300

Which of the following reports the relative strength of an ultrasound wave?

a. Decibels

b. Watts

c. W/cm^2

d. Pascals

a. Decibels
300

Half value layer depends upon which of these features?

a. path length and frequency

b. path length and propagation speed

c. medium and frequency

d. PRF and medium

C. medium and frequency
300

To calculate the acoustic impedance of a medium, one should ___ the ___ by the ____.

a. divide, propagation speed, density

b. multiply, density, propagation speed

c. divide, density, propagation speed

d. multiply stiffness, density

b. multiply, density, propagation speed
300

An ultrasound wave travels strikes an interface between two media at a 90 degree angle. The propagation speeds of the media are identical. However, the densities of the media are different. Which is true?

a. reflection will definitely occur

b. reflection will definitely not occur

c. refraction may occur

d. none of the above

a. reflection will definitely occur
400

Which of the following values can correctly designate both the duty cycle and the beam uniformity coefficient?

a. 1%

b. 0

c. 100%

d. None of the above

c. 100%
400

The intensity of an ultrasound wave is changed by -6dB. This means that the current intensity is ___ as much as its original level.

a. One-tenth

b. Four times

c. One-fourth

d. One-sixth

C. One-fourth
400

Which of the following is not one of the physical processes that contribute 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
400

A sound wave strikes a boundary between two media at a 60 degree angle. This is called ____ incidence.

a. orthogonal

b. angular

c. obtuse

d. oblique

d. oblique
400

True of False? When reflection occurs with oblique incidence, the angle of reflection equals the angle of incidence. This is known as Snell's Law.

False.
500

Two acoustic beams have identical SPTP intensities of 400 mW/cm2. One beam is pulsed while the other is continuous wave. Which beam has a higher SPTA intensity?

a. The pulsed beam

b. The continuous wave

c. Neither

d. Cannot be determined

b. The continuous wave
500

A sound wave with 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%.
500

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. path length and frequency of sound
500

Which value is closest to the impedance of soft tissue?

a. 1.5 kiloRayls

b. 2.5 deciRayls

c. 19 megaRayls

d. 2,000,000 Rayls

d. 2,000,000 Rayls

The impedance of soft tissue is in the range of 1.5 to 2.5 million Rayls

500

A sound pulse strikes a boundary between two media with normal incidence. The speed of sound in the two media are very different; however, the impedances of the media are identical. What will happen?

a. a big echo will be produced

b. a medium echo will result

c. a small echo will result

d. there will be no echo at all

d. there will be no echo at all