Lesson 2: Basic Principles of Acoustics

Question 1

By changing the transducer, the ultrasonic testing technician could change the testing:

a. frequency.

b. reject level.

c. electrical pulse voltage.

d. pulse repetition rate.

Question 2

Another name for a longitudinal wave is:

Question 3

The velocity of a longitudinal wave in steel is:

Question 4

Surface waves travel at about 10% less than:

a. longitudinal waves.

b. compression waves.

c. plate waves.

d. shear waves.

Question 5

In ultrasonic testing, the term attenuation is closely connected to:

a. velocity.

b. efficient transmission.

c. damping.

d. refraction.

Question 6

When wave energy is lost through reflection and scattering of the beam within the material, it is understood that __________ is occurring.

a. molecular interference

b. high density obstruction

c. high frequency subversion

d. attenuation

Question 7

The opposition of a material to the passage of a sound wave is called:

a. acoustic impedance.

b. acoustic velocity.

c. viscosity.

d. refraction.

Question 8

Acoustical impedance of a given material is derived by material density:

a. divided by sound velocity.

b. multiplied by sound velocity.

c. minus sound velocity.

d. plus sound velocity.

Question 9

The higher the ratio of acoustic impedance, the:

a. greater the reflectivity of an interface between two different materials.

b. lower the attenuation.

c. greater the acoustic velocity.

d. greater the frequency.

Question 10

A higher impedance ratio is often called impedance:

a. mismatch.

b. emissivity.

c. reflectivity.

d. tolerance.

Question 11

In ultrasound, the term refraction refers to ________ of the sound beam as it passes from one medium to another.

a. acceleration

b. bending

c. depletion

d. slowing

Question 12

Refraction and mode conversion occur because the ____________ of the longitudinal wave changes as the beam enters the second medium.

a. speed

b. vibration

c. oscillation

Answer 12

Speed

Question 13

The velocity of shear waves is approximately that ________ of compression waves.

Answer 13

Half

Question 14

The point at which the longitudinal wave refracts to 90° is called the ________ angle.

Question 15

The region between normal incidence and the first critical angle is not very useful for ultrasonic testing purposes because:

a. the presence of two beams results in confusing reflections.

b. there is a need for another beam to have reliable reflections.

c. the shear wave has not obtained peak energy at this point.

d. the region is too weak for ultrasonic testing