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