Give the units of measure for each term below.
a. wavelength
b. frequency
c. intensity
d. propagation speed
e. period
f. power
a. millimeters - wavelength
b. Hertz - frequency
c. watts/cm2 - intensity
d. meters/sec - propagation speede. second - periodf. watts - power
Which of the following cannot be changed by the sonographer?
A. wavelength
d. propagation speed
e. sound source
True or False?
Sound is a transverse, mechanical wave.
FALSE: Sound is mechanical, but it is a longitudinal wave.
True of False?
A wave with a frequency of 15,000 MHz is ultrasonic.
TRUE: Ultrasound is defined as any wave with a frequency exceeding 20,000 hertz. In this example, the wave's frequency is 15,000MHz or 15,000 million hertz.
True or False?
If the amplitude of a wave is increased to 3 times its original value, the intensity is increased by 6 times.
FALSE: Intensity is proportional to the amplitude squared. If amplitude is tripled, the intensity is increased by a factor of nine.
True or False?
If the power of a wave is halved, the intensity is reduced to one-fourth its original value.
Intensity is proportional to the power. If the power is divided in half, the intensity will also be half as great.
True or False?
Propagation speed increases as frequency increases.
FALSE: Propagation speed is determined only by the medium. Frequency does not affect the propagation speed.
Which of the following are considered acoustic variables?
a. frequency
b. density
c. particle motion
d. temperature
e. period
f. pressure
b,c,d, and f: Density, particle motion, temperature, and pressure
How many cycles occur in 0.5 seconds if the frequency is 5 million Hz?
2,500,000 cycles
Two sound beams with different frequencies are traveling through the same medium. Are the following parameters larger, smaller, or the same for the wave with the higher frequency?
a. wavelength
b. propagation speed
c. period
d. amplitude
a. wavelength = smaller
b. density = same
c. particle motion = smaller
d. temperature = same
The effects of ultrasound upon tissue are called _____ .
biologic effects
What is the acoustic velocity in soft tissue?
In soft tissue, sound travels 1.54 km/sec or 1,540 m/s.
Which medium has a lower propagation speed?
Medium 1 has a density of 9 and a stiffness of 6.
Medium 2 has a density of 8 and a stiffness of 6.
Medium #1 has the lowest propagation speed. Since the stiffness of the two media are the same, the medium witht the GREATER density has the LOWER propagation speed.
All of the following may be units of amplitude except:
B. m/s Meters per second are units of speed. Speed is not an acoustic variable.
How are the following parameters related- directly, inversely, or unrelated?
a. Frequency and Period
b. Amplitude and Power
c. Amplitude and Intensity
d. Power and Intensity
e. Wavelength and Intensity
f. Wavelength and Frequency
RELATIONSHIP
a. Frequency and Period = inversely
b. Amplitude and Power = directly
c. Amplitude and Intensity = directly
d. Power and Intensity = directly
e. Wavelength and Intensity = unrelated
f. Wavelength and Frequency = inversely
How are the following parameters related- directly, inversely, or unrelated?
a. Acoustic Velocity and Density
b. Elasticity and Speed of Sound
c. Acoustic Velocity and Compressibility
d. Stiffness and Sound of Speed
e. Frequency and Sound Speed
f. Frequency and Intensity
g. Power and Frequency
RELATIONSHIPa. Acoustic Velocity and Density = inversely
b. Elasticity and Speed of Sound = inversely
c. Acoustic Velocity and Compressibility = inversely
d. Stiffness and Sound of Speed = directly
e. Frequency and Sound of Speed = unrelated
f. Frequency and Intensity = unrelated
g. Power and Frequency = unrelated
_____ is the time from the start of a pulse to the end of that pulse.
Pulse Duration
_____ is the time from the start of a pulse to the start of the next pulse.
Pulse Repetition Period
Pulse Repetition Frequency is the reciprocal of _____ .
Pulse Repetition Period
By changing the imaging depth, which of the following parameters does the operator also change?
a. Pulse Repetition Frequency
b. Duty Factor
c. Propagation Speed
d. Pulse Repetition Period
e. Amplitude
f. Spatial Pulse Length
a. Pulse Repetition Frequency
b. Duty Factor
c. Pulse Repetition Period
The speed of a 5 MHz continuous wave is 1.8 km/sec in a particular medium. If the wave is then pulsed with a Duty Factor of 0.5, calculate the new propagation speed?
The propagation speed depends only upon the medium through which the sound travels. The new propagation speed is exactly the same as the old propagation speed, 1.8 km/sec.
Which of the following parameters can be changed by the sonographer?
D. Pulse Repetition Period (PRP): PRP comprises the transmit and receive times. The sonographer adjusts the receive time and therefore adjusts the PRP.
All of the following are determined solely by the US system and not the medium except:
C. Spatial Pulse Length: The SPL is determind by both the source and the medium.
