Ch. 3 Period and Frequency
Which of the following can not be considered a unit of frequency?
cycles
What term describes the number of cycles that an acoustic variable completes in a second?
frequency
Ultrasound is defined as a sound with a frequency of:
greater than 0.02 MHz
What is characteristic of acoustic waves with frequencies less than 20 Hz when compared with waves having frequencies of more than 20 Hz?
humans cannot hear them
What is the characteristic of acoustic waves when frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000 Hz?
humans cannot hear them
With standard ultrasonic imaging, what happens to the period of a wave as it propagates?
remains the same
What determines the period of an ultrasound wave?
the transducer
What establishes the frequency of an ultrasound wave?
the transducer
The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer.
False
If the periods of two waves are the same, then the frequencies of waves must also be the same.
True
Infrasound is defined as a sound with a frequency of:
less than 20 Hz
What is the range of periods commonly found in waves produced by ultrasound systems?
0.1 to 0.5 microseconds
What is the range of frequencies emitted by transducers used in ultrasonic imaging?
2,000,000 to 15,000,000 Hz
Which of the following waves is ultrasonic and least useful in diagnostic imaging?
24 kHz
Compare two sound waves A and B. The frequency of wave A is one third that of wave B. How does the period of wave A compare with the period of wave B?
A is three times as long as B
With standard ultrasound pulses, the frequency of the ultrasound changes significantly as the wave propagates through the body.
False