Ultrasound Physics: Period and Frequency (Chapter 3 Part 1)

Ultrasond is defined as a sound with a sound frequency of ____. A. greater than 20,000 kHz B. less than 1 kHz C. greater than 10 MHz D. greater than 0.2 MHz

D. greater than 0.2 MHz (0.2 MHz, 20,000 Hz or 20 kHz)

Which of the following CANNOT be considered a unit of frequency? A. per day B. cycles/sec C. Hz D. hertz E. cycles

E. cycles

True or False? The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer.

False

Which of the following units are appropriate to describe the period of an acoustic wave? A. minutes B. microseconds C. meters D. mm/us E. cubic centimeters

A and B (minutes and microseconds)

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 transducer

What establishes the frequency of an ultrasound wave? A. the transducer B. the medium through which the sounds travels C. both A and B D. neither choice A or B

A. the transducer

What is the range of periods commonly found in waves produced by ultrasound systems? A. 0.001 to 1 s B. 0.06 to 0.5 us C. 0.2 to 1 ms D. 10 to 100 ns

B. 0.06 to 0.5 us

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. frequency

Infrasound is defined as the sound with a frequency of ____. A. greater than 20,000 Hz B. less than 20 Hz C. greater than 10 MHz D. less than 0.2 MHz

B. less than 20 Hz (Infrasound is defined as an acoustic wave with a frequency so low that it is not audible to humans.)

The frequency of a CW is 5 MHz. The wave is the 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. 5 MHz (Frequency is the reciprocal of 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.)

Compare two sound waves, A and B. The frequency of wave A is one-third the top 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. A is three times as long as B (Frequency and period are reciprocals. If the frequency of one wave is one-third as large as the other, then the period of the wave will be three times longer than the other.)

____ is the reciprocal of period. A. inverse period B. PRP C. frequency D. propagation speed

C. frequency

With standard ultrasonic imaging, what happens to the period of a wave as it propagates? A. increases B. decreases C. remains the same

C. remains the same

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. remains unchanged

What is the range of frequencies emitted by transducers used in ultrasonic imaging? A. 1 to 3 MHz B. 1 to 1,000 kHz C. -10,000 to +10,000 Hz D. 2,000,000 to 15,000,000 Hz

D. 2,000,000 to 15,000,000 Hz (or 2 to 15 MHz)

What is characteristic of acoustic waves with frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000 Hz? A. they travel more effectively in soft tissue B. they travel more rapidly C. they attenuate less when traveling in soft tissue D. humans can't hear them

D. humans can't hear them

What is characteristic of acoustic waves with frequencies of less than 20 Hz when compared to 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 can't hear them

D. humans can't hear them

True or False? With standard ultrasound pulses, the frequency of the ultrasound changes significantly as the wave propagates the body.

False

True of False? If the period of two waves are the same, then the frequencies of the waves must also be the same.

True

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 continuous?

True

True or False? Waves in the ultrasound range behave in the same general manner as sound waves that are audible.

True