Chapters 6-8 Study Guide

Question 1

A logarithmic scale is associated with

Answer 1

Decibel notation

Question 2

The decibel notation for an acoustic signal that has attenuated would be

Answer 2

Negative

Question 3

A ____ change in a value intensity means that the value has doubled.

Answer 3

3 dB

Question 4

Attenuation is determined by

Answer 4

Path length and the frequency of sound.

Question 5

Rayleigh scattering is related to

Answer 5

Frequency to the 4th power

Question 6

Rayleigh scattering defined

Answer 6

Uniform dispersion of a sound wave in many different directions after striking a very small particle.

Question 7

A sound beam travels ___ in soft tissue.

Answer 7

7cm

Question 8

The attenuation coefficient is __.

Answer 8

3 dB/cm

Question 9

What is the total attenuation that the sound beam experienced?

Answer 9

7 x 3 = 21 dB

Question 10

The attenuation traveling through bone is _____ than its attenuation through soft tissue.

Answer 10

Greater

Question 11

Attenuation through lung tissue is ____ than soft tissue.

Answer 11

Greater

Question 12

Sound traveling through blood attenuates

Answer 12

To a lesser extent than when traveling through soft tissue.

Question 13

Impedance is a property of the medium and has units of ____.

Answer 13

Rayls

Question 14

To calculate acoustic impedance

Answer 14

Multiply the density by the propagation speed.

Question 15

___Angles are less than ___ degrees.

Answer 15

Acute,90

Question 16

___Angles are greater than ____ degrees.

Answer 16

Obtuse,90

Question 17

Angles with a measure other than 90 are called

Answer 17

Oblique angles

Question 18

Intensity transmission coefficient + ________ = 1.

Answer 18

Intensity reflection coefficient

Question 19

Does intensity reflection coefficient have any associated units?

Answer 19

No.

Question 20

When will reflection occur

Answer 20

When a sound beam strikes a tissue boundary at 90 degrees & media on either side of the boundary will have different impedances.

Question 21

For refraction to occur at a boundary between 2 media there must be

Answer 21

Dissimilar propagation speeds and oblique incidence.

Question 22

Backscatter reflection occurs when

Answer 22

A sound wave reaches a rough or irregular border between 2 media.

Question 23

Snell’s law governs ____

Answer 23

Refraction

Question 24

The ultrasound systems electronics determine the

Answer 24

Frequency of the sound produced by the transducer of a continuous wave system.

Question 25

What would cause a PZT crystal to lose its special properties?

Answer 25

Exposure to high temperatures

Question 26

Order of impedance from highest to lowest

Answer 26

PZT, matching layer, gel, skin.

Question 27

Dampening material of an ultrasound transducer is made from

Answer 27

A slab of epoxy embedded with tungsten particles.

Question 28

The purpose of the backing material of an ultrasound transducer is to

Answer 28

Shorten the pulses, thereby creating images with better image quality.

Question 29

The active element thickness is

Answer 29

1/2 the wavelength of the soundwave in the PZT

Question 30

Decibel notation can be described as

Answer 30

The ratio between 2 numbers.

Question 31

Attenuation coefficient is

Answer 31

The amount of attenuation per cm that a sound wave undergoes.