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Sound is classified as __________ energy.
mechanical
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The general oscillatory movement of the molecules in respone to the interation of ultrasound energy is called _______ _________ _______.
simple harmonic motion
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In the medium, one area of increased pressure is called _______.
compression
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In a medium, one area of decreased pressure is _________.
rarefaction or decompression
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What is the type of wave motion where the molecules oscillate in the same direction as the sound energy travel?
longitudinal
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Longitudinal oscillatory motion most frequently occurs in what type of medium?
soft tissue
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What is the type of wave motion where the molecules oscillate at 50 degrees relative to the direction of sound energy propagation?
shear waves
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Shear waves most frequently occur in what kind of medium?
solids (bone)
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What is the definition of a cycle?
One area of compression + one area of rarefaction.
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What is the definition of frequency?
Number of cycles per second.
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What is the unit of measurement of frequency?
Hertz
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What are the categories within the sound spectrum?
- INFRA: below 20Hz
- AUDIBLE: 20-20,000Hz
- ULTRA: above 20,000Hz
- DIAGNOSTIC: 2.25MHz & up
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What is the definition of period?
The time it takes for one cycle to occur.
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What is the definition of wavelength?
The distance that one cycle travels.
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What is the definition of amplitude?
maximum pressure variation in a cycle (the strength of the wave) aka the pressure gradiant
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What is the definition of power?
Rare that energy is transferred (controlled by the acoustic power control)
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What is the equation that demonstrates the relationship between power and intensity?
power = intensity
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What is the equation that demonstrates the relationship between power and amplitude?
power = amplitude2
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What is the equation that demonstrates the relationship between intensity and amplitude?
intensity =amplitude2
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What are the units of measurement for power, intensity, and amplitude in clinical aplications?
- power: watts
- intensity: watts/cm2
- amplitude: dB (decibels)
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If the amplitude is increased by a factor of 3, the power is increased by a factor of __.
9
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If the power is increased by a factor of 3, the intensity increases by a factor of __.
3
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If the amplitude is increased by a factor of 4, the intensity increases by a factor of __.
16
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If the beam area is reduced to 1/2, the intensity equals __.
x 2
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Decreasing the intensity to 1/8 of the original intensity = ___ dB.
-9
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Decreasing the intensity to 1/4 of the original intensity = __ dB.
-6
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Decreasing the intensity to 1/2 of the original intensity = __ dB.
-3
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Decreasing the intensity by a factor of 10 = __ dB.
-10
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Increasing the intensity by a factor of 10 = ___dB.
10
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Doubling intensity = ___ dB.
3
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Increasing intensity by a factor of 4 = ___ dB.
6
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Increasing intensity by a factor of 8 = ___ dB.
9
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What is the definition of intensity?
Power of sound field divided by beam cross section area.
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The propagation speed is slowest in what type of medium?
gas
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The propagation speed is fastest in what type of medium?
solid
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What is the average propagation speed in soft tissue?
1.54 mm/μs or 1540 m/s
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Soft tissue is classified as what type of medium - gas, liquid, or solid?
liquid
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What is the mathematical relationship between wavelength and frequency?
λ=  or λ= because c (propagation velosity) is a constant... ALWAYS 1.54mm/μs
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What are the primary characteristics of the medium that determine the propagation speed? What is the mathematical relationship?
- density and elasticity
- c=E/ρ or propagation speed=elasticity/density
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If the wavelength is doubled, the frequency will ____.
decrease by 1/2
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What is the mathematical relationship between frequency and period?
inverse
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If the frequency is reduced to 1/2, the period will ____.
increase by 2
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What is the mathematical relationship between period and frequency?
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propagation velocity = _______ x wavelength
frequency
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What is the average propagation speed for gasses, liquids and solids?
- gas: 400 m/s
- liquid: 1540 m/s
- solid: 4000 m/s
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What does the log equation do?
- Allows us to convert intensity into dB notation. This provides a standard measurement for intensity on all equipment.
- dB= 10 log10 (I1/I0)
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What are the clinically relevant metric units?
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What is the order of metric units using 1 meter as the base unit.
- 1000000000nm (nanometers)
- 1000000μm (micrometers)
- 1000mm (millimeters)
- 100cm (centimeters)
- 1m (meter)
- .001km (kilometers)
- .000001Mm (megameters)
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Intensity is equal to Power divided by the _______.
Beam Area
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What are the clinically relevant measurements for frequency, wavelength, and period?
- frequency = MHz
- wavelength = mm
- period = μs
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What are the mathematical relationships between frequency and λ, frequency and period?
- frequency and wavelength are inversely related
- frequency and period are inversely related
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What information must be known in order to convert intensity into dB?
two intensity levels f1 and f0
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