Sonography Principles and Instrumentations (SPI) Examination Outline 2024 questions and answers.
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Course
Sonography
Institution
Sonography
Sound
- a form of mechanical energy produced by vibrating objects that is transmitted by pressure waves through a medium
- needs a medium with particles to travel/propagate
- cannot travel in a vacuum (medium with no particles)
Mechanical Energy
- has to be transmitted
- propagate...
Sonography Principles and
Instrumentations (SPI)
Examination Outline 2024
questions and answers
\Sound
- a form of mechanical energy produced by vibrating objects that is
transmitted by pressure waves through a medium
- needs a medium with particles to travel/propagate
- cannot travel in a vacuum (medium with no particles)
Mechanical Energy
- has to be transmitted
- propagated from one point to another
- need a medium (can't propagate without a medium)
Cycle
- used to describe any changes in particle motion (particle
displacement, density, or molecules, pressure, and particle velocity)
that takes place at regular intervals
Acoustic Variables
- used to distinguish between sound waves and other types of
waves
FOUR Acoustic VARIABLES
- pressure
- density
- particle motion (distance and temperature)
Pressure (p)
,- concentration of force per unit of area (per unit meter squared)
- units: Pascals (Pa)
Density (ρ)
- concentration of mass in a volume
- unit: kilograms per centimeter cubed (kg/cm^3)
Density of Human Blood
- 1.05 g/mL of volume
Density of Water
- 1.0 g/mL of volume
Distance (d)
- measure of particle motion
- units: mm, cm, feet
Sound waves consist of..
- Compression
- Rarefraction
Compression
- regions of high pressure and density
- physical region of matter that has been disturbed due to elastic
distortion
- increases in any acoustic variables cause the sound waves to be
compressed
Rarefractions
- regions of low pressure and density
- decreases in any of the acoustic variables cause the sound waves
to be refracted
Transverse Wave
- particles move in a direction that is PERPENDICULAR (at right
angles) to the direction that the wave propagates
- example: ocean wave
Longitudinal Wave
,- particles move in the SAME DIRECTION/PARALLEL that the wave
propagates
- sound is a longitudinal wave form
- example: acoustic wave
The Nature of Sound
- only a LONGITUDINAL waveform that travels in a STRAIGHT line in
time and space
- cannot be transverse
Interference
- when waves lose their individual characteristics at that moment
and combines to form a single wave
In-Phase Interference
- constructive, 2 or more waves are combined to form one larger
wave
- a pair of waves when their peaks (maximum values) occur at the
same time and at the same location
- the troughs (minimum values) occur at the same time and place
Out-of-Phase Interference
- destructive, 2 or more waves are combined to form one smaller
wave
- their peaks occur at different times and places
Destructive Interference
, - the resultant wave is SMALLER than of its components (out-of-
phase waves)
Constructive Interference
- the resulting wave is LARGER than either of its components (in-
phase waves)
Acoustic Parameters
- describe features of a sound wave
- seven parameters are required to completely characterize a sound
wave
SEVEN Acoustic PARAMETERS
1. Period
2. Frequency
3. Amplitude
3. Intensity
5. Power
6. Wavelength
7. Propagation Speed
Period (T)
- the TIME IT TAKES A WAVE TO VIBRATE A SINGLE CYCLE, or the
time from the START OF ONE CYCLE TO THE START OF THE NEXT
- units: microseconds
- typical value: 0.07-0.5 microseconds
- determined by the sound source ONLY
- CANNOT be changed by the sonographer
Frequency (f)
- the number of particular events that occur in a specific duration of
time; the NUMBER OF CYCLES (pressure oscillations)
occurring IN ONE UNIT OF TIME
- units: Hertz (Hz)
- typical value: 2MHz-15MHz (complimentary unit of hertz is seconds
and complimentary unit for kilohertz is a millisecond)
- determined by the sound source ONLY, not the medium through
which sound is traveling
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