Questions and Answers
What is the unit of sound intensity named for?
Alexander Graham Bell
What is a decibel a relationship between?
Two values of power
In diagnostic ultrasound, decibels are used for what?
Attenuation, gain and dynamic range
What happens to sound as it travels in the body?
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What happens to a sound wave after it is received by the transducer?
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What is the standard measurement tool for sound intensity?
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Decibels are based on what mathematical construct?
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What do decibels measure?
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How many intensities are needed in order to use decibels?
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What are the two intensities used in decibel measurement?
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What does decibel (dB) measure?
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The logarithmic relationship of decibels allows large ranges of sound intensity to be handled in more manageable units.
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What does the log of a number represent in terms of powers of 10?
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To obtain the number 100, what multiplication is done using 10?
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In logarithms, when they say 'increase', what does it refer to?
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What does the Richter scale measure?
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What is the log of 1000?
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For powers of 10, what can you do?
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What is decibel notation?
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Decibel notation measures absolute numbers.
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What do positive decibels report?
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When a wave intensity doubles, what is the relative change in decibels?
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If the decibel is positive, what does it indicate about the unit?
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What portion does -10 dB represent in terms of original power?
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If intensity or amplitude has a factor of 4, how many decibels is that?
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A bee's buzz is often rated with a decibel rating of 40 dB. Normal conversation is rated at 60 dB. How many times more intense is normal conversation compared to a bee's buzz?
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Study Notes
Units of Sound Intensity
- Bel: A unit named after Alexander Graham Bell, used to measure sound intensity.
- Decibel (dB): Represents a relationship between two power values, typically used in sound measurements.
Application in Diagnostic Ultrasound
- Decibels measure attenuation, gain, and dynamic range in ultrasound.
- Sound weakens as it travels through the body, requiring amplification after being received by the transducer.
Decibel Notation
- Standard Measurement: Decibel notation is a logarithmic scale.
- Based on logarithms, where log of a number signifies how many times 10 is multiplied to achieve that number.
- Decibels do not measure absolute sound levels but relative changes.
Positive and Negative Decibels
- Positive decibels indicate increasing signal strength, with specific correlations for intensity changes (e.g., +3 dB means double the intensity).
- Negative decibels reflect a decrease in intensity, with -3 dB signifying a reduction to half the original value.
Decibel Values and Relationships
- Each doubling of sound intensity corresponds to an increase of 3 dB.
- A 10-fold increase results in a 10 dB increase.
- Calculating relative changes: A factor of 4 results in an increase of 6 dB, while a reduction to one-tenth is expressed as -10 dB.
Examples of Sound Intensity Changes
- A sound intensity increase by a factor of 16 corresponds to a 12 dB increase (4 doublings).
- The comparative intensity of sounds can be assessed: normal conversation at 60 dB is 100 times more intense than a bee's buzz at 40 dB.
Practical Applications and Measurements
- Decibels facilitate managing large ranges of sound intensity. For powers of 10, counting zeros determines the logarithmic increase.
- Sound intensity is proportional to the square of the amplitude; quadrupling amplitude increases intensity by a factor of 16.
Miscellaneous
- Richter Scale: Another application of logarithmic measurement, used to quantify earthquake magnitudes.
These notes provide a concise overview of the principles and applications of decibels in sound intensity measurement and related concepts.
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Explore key terms and definitions related to decibels through these flashcards. Learn about the unit of sound intensity, its applications in diagnostic ultrasound, and how sound weakens as it travels through different media. Perfect for students seeking to understand sound measurement concepts.
