Sound Waves Flashcards
______ is the time of the start of one cycle to the start of the next.
PERIOD
What is the unit of period?
Time; seconds, milliseconds (mm)
With diagnostic ultrasound what are the value of period?
one-tenth to one-half millionth of a second.
What is period determined by?
Sound source only
Can period be adjusted?
No
_______ is the number of cycles that occur in one second?
Frequency
What are the units of frequency?
Hertz (Hz)
Convert the following to Hz.
1. 5 cycles/ second
2. 5,000 cycles/ second
3. 5,000,000 cycles/ second
- 5 Hz
- 5 KHz
- 5 MHz
What is the typical frequency range of ultrasound in a clinical setting?
2Mhz-15Mhz
What is frequency determined by?
Sound source only
Is frequency adjustable?
No
What is the equation for frequency?
Frequency= cycles/ second
If there are 10 cycles in 5 seconds, What is the frequency?
10/5=2
2Hz
How many Hz is below human hearing?
Less than 20 Hz
What does inaudible mean?
Can’t be heard
What is the frequency of an infrasonic sound wave?
Less than 20 Hz
What is the frequency of an audible sound wave?
Between 20 Hz and 20 KHz
What is the frequency of ultrasound?
Greater than 20 KHz
What is a frequency so high, humans can’t hear?
Ultrasonic
What is the relationship between frequency and period?
Inversely related
True or False. Are frequency and period reciprocals?
TRUE
True or False. The lower the frequency the longer the period?
True
Period X Frequency=1
Do higher or lower frequencies have shorter periods?
Higher frequencies
Does a wave with a longer or shorter period have have a lower frequency?
Longer period
What are the three parameters that describe size and strength of a sound?
Amplitude
Intensity
Power
What term describes the difference between the maximum value and average value of an acoustic wave?
Amplitude
What is amplitude describing when discussing a wave?
Bigness of a wave
What are the units for amplitude?
Pressure (Pascals)
Density ( g/cm3)
distance (inches, cm)
What is amplitude expressed in?
Decibels (Db)
What are the typical values of amplitude in the clinical setting?
1MPa-3MPa
What determines amplitude
Sound source orginally
Is amplitude adjustable?
YES
How is amplitude measured?
From the baseline to the maximum or minimum value
What is the difference between maximum and minimum values of an acoustic variable?
Peak-to Peak amplitude
What is twice the value of amplitude?
Peak-to-Peak amplitude
What is the rate of energy transferred?
Power
What describes the bigness of a wave?
Power
Amplitude
Intensity
How is power and amplitude related?
Directly related
What are the units of Power
Watts
What is power proportional to?
Amplitude to the 3rd power
What is power proportional to?
Amplitude
What is power determined by?
Sound source only
How is power related to frequency?
unrelated
Does power increase or decrease as it propagates through tissue?
Decreases
What determines the rate at which power decreases as sound travels through the body?
Characteristics of the medium and wave
Is power adjustable?
Yes
What does power equal?
Amplitude2
If you increase the amplitude by a factor of 2 how does has power changed?
Power has increased 4 fold.
(2x2=4)
If you decrease the amplitude 1/4 its original value, how has power changed?
Power has decreased 1/16
(1/4 x1/4= 1/16)
What is the concentration of energy in a sound beam?
Intensity
How is intensity calculated?
Power/area
What does intensity depend upon?
Power and area
What are the units of power?
W/cm2
What is intensity determined by?
Sound source
What determines how the rate of intensity changes as it travels through the body?
Characteristics of the medium and shape of the sound beam
Is intensity adjustable?
Yes
How is intensity related to frequency?
unrelated