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Cards In This Set
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This is a technique of rating numbers.
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Logarithms
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The logarithm of any number represents the number of times that "10" has to be multiplied together to create the original number. What is the Log of 100?
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The log of 100 is 2.
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What is the Log of 1000?
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The log of 1000 is 3. (10x10x10)
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This is known as a logarithmic scale.
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Decibels are known as a logarithmic scale. It's a relative scale - ratio of the final to the initial strengths. Two intensities are needed to calculate decibles.
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What are the units of relative amplitude?
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Decibles.
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A component of an ultrasound system increases a signal's power from 1 watt to 100 watts. How is this expressed in decibels?
a) 10dB b) 40dB c) 6dB d) 20dB e) 100dB
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D. The final signal is 100 times bigger than the initial. 100 is 10x10. Each 10 fold increase means 10 dB, so this is 20 db.
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The power of a system is at 100% and this is 0dB. What is the change in dBs when the system's power is at 50%?
a)-10dB b)-50dB c) -3dB d) 3dB e) 50dB
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C. The system's power has been halved, -3dB means half.
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A component of an ultrasound system increases a signal's power from 5 to 500 watts. How many decibels is this?
a) 10dB b) 40dB c) 6dB d) 20dB e) 100dB
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D. The final signal is 100 times bigger than the initial. 100 is 10x10. Each 10 fold increase means 10 dB, so this is 20 dB
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A reduction of intensity to one-half of its original value is_______db?
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-3db
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A drop in intensity to one-quarter of its original value is _____dB?
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-6 dB
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-10dB means that the intensity is reduced to ______ of it's original value.
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1/10th of it's original value
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DB is a mathematical representation with a _________ scale.
a) muliplicative
b) division
c) longitudinal
d) logarithmic
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D. Logarithmic
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True or False.
We need one intensity to calculate decibels?
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False. Two intensities or two ratios are needed to calculate decibels.
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The initial intensity of a wave is 2mW/cm2, and ther eis a change of 9dB. What is the final intensity?
a) 6mW/cm2
b) 2mW/cm2
c)16mW/cm2
d) 8mW/cm2
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The answer is C. 2x8=16
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Every 3 dB means that the intensity will ______?
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Double (2x2x2)
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