Ch.3 Physics Flashcards
Hz is per
second
Period has an inverse/reciprocal relationship with
frequency
Describes features of a sound wave
parameters
Time it takes a wave to vibrate in a single cycle
period
Units for period
time
Period is determined by
sound source
Is period adjustable
no
What is the source of a sound wave
ultrasound system and transducer
Number of particular events that occur in a specific duration of time
Frequency
Frequency is reported in
units per second, hertz
Typical value for frequency
2-15 MHz
Frequency is determined by
sound source
Is frequency adjustable
no
Frequency of infrasound
less than 20 Hz
Frequency of audible sound
between 20Hz and 20Khz
Frequency of ultrasound
greater than 20 KHz
What is the relationship between frequency and period
inversely related/reciprocal
Period x Frequency=
1
Which parameters are the “bigness” parameters
amplitude power intensity
Difference between maximum value and average or undisturbed value of an acoustic variable
amplitude
amplitude units
acoustic variables: pressure, density, distance
Amplitude is determined by the
sound source
Is amplitude adjustable
yes
Measured from middle value to the max value
amplitude
Difference between max and min values of an acoustic variable
peak-to-peak amplitude
Rate of energy transfer or which work is performed
power
Units of power
watts
Initial power is determined by
sound source
Is power adjustable
yes
Equation for relation between amplitude and power
power (proportional to) amplitude^2
As power increases, amplitude
increases
Concentration of energy in a sound beam
Intensity
Intensity units
watts/cm^2 (power and area)
Intensity is determined by
sound source
Is intensity adjustable
yes
Equation for intensity
Intensity=(power/area) w/cm^2
Intensity is _____ to power
directly proportional
Intensity is ____ to amplitude ______
directly, squared
Distance or length of one complete cycle
wavelength
wavelength units of
length
In clinical imaging, wavelength is soft tissue ranges from
0.1 to 0.8 mm
Wavelength is determined by
sound source and medium
Is wavelength adjustable
no
Wavelength refers to _____ as period refers to ____
length, time
Wavelength and frequency are _____ related
inversely
Wavelength equation
wavelength (mm)=(1.54mm/microsec) / Frequency MHz
Rate at which a sound wave travels through a medium
propagation speed
Speed is units of
any distance divided by time (m/sec)
Speed is determined by
medium
Is speed adjustable
no
What is the speed of sound in soft tissue
1540 m/sec
Sound travels ______ in solids, ____ in liquids and ____ in gases.
fastest, slower, slowest
What 2 characteristics of a medium affect the speed of sound
stiffness and density
Describes the ability of an object to resist compression
stiffness
Describes the relative weight of a material
Density
How does stiffness affect speed
directly related
How does density affect speed
inversely related
