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17 Cards in this Set
- Front
- Back
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What does an amplifier do?
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increases voltage amplitude
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What is amplification?
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the conversion of the small voltages received from transducer elements to larger ones suitable for further processing and storing
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What is amplitude?
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the strength of the detected echo or the voltage induced in a crystal by a pressure wave
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What is attenuation?
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decrease in intensity as a sound beam travels through the medium
(some energy is scattered, reflected, or absorbed) increase frequency, increase attenuation |
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What is a decibel?
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unit to express relative intensity
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What is frequency defined as?
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number of cycles per unit time
lower frequency penetrates deeper higher frequency attenuates faster higher frequency provides better resolution units: Herz |
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What is intensity?
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Power per unit area
describes the amount of energy flowing through a unit cross-sectional area of a beam each second units: dB |
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What is power?
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energy per unit area
measure of the total energy transmitted summed over the entire cross-sectional area of the beam per unit time units: Watt |
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What is a transducer?
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Device that converts one form of energy into another form
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What do longitudinal waves do?
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propagate by the particles of the medium in the same direction as (or parallel with) the wave propagation
aka particles move in same direction as energy flows |
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Define sound.
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radiant mechanical energy that is transmitted by longitudinal pressure waves in a material medium
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What does "radiant energy" imply?
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that the energy travels in waves
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What is the acoustic spectrum?
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infrasound < 20 Hz
audible sound 20 - 20,000 Hz ultrasound > 20,000 Hz yeah...doesn't make sense that its different than radiation physics huh |
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What are 3 differences between ultrasound and electromagnetic radiation?
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ultrasound - speed depends on medium, requires a medium, longitudinal wave
electromagnetic radiation - speed of light, no medium required, transverse wave |
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What are some commercial uses of ultrasound?
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military sonar
fishing mapping ocean floor study of marine life detection of flaws in metals |
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What are the primary effects of ultrasound on the medium with which it interacts?
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-absorbed to create heat
-reflects back to probe or scatters throughout the tissue -refracted in another direction |
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What is important about a piezoelectrical crystal?
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it transforms energy (electrical to mechanical, vice versa)
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