Chapters 5-8 Jessica Flashcards
What is the log of 1000
3
A drop in intensity to one quarter of its original value is _______ dB?
6
dBs represent a ______ change in intensity?
relative
If the initial intensity is less than the final intensity, then the gain in dB is ______(+or-)?
positive
-10 dB means that the intensity is reduced to ____ of its original value?
one-tenth
Which of the following has greater attenuation?
a. long distance, low frequency
b. long distance, high frequency
c. short distance, low frequency
d. short distance, high frequency
b
Which of the following results in the most attenuation?
a. 4MHz, 2 cm path length
b. 4 MHz, 8 cm path length
c. 6 MHz, 8 cm path length
d. 6 MHz, 4 cm path length
c
As frequency increases, attenuation coefficient____?
increases
What is the unit for impedance?
Rayls (Z)
What are the 3 components of attenuation?
absorption, reflection, scattering
What component of attenuation is the dominant contributor to attenuation?
Absorption
Total attenuation is related to ____ and _____?
path length and frequency
Attenuation in air is ____ than in soft tissue?
much greater than
What are the units of attenuation?
dB
As the path length increases, the attenuation coefficient _____?
remains the same
Attenuation coefficient is directly related to____?
frequency
Rayleigh scattering is related to _____?
frequency^4
A sound wave with an intensity of 75 W/cm-squared, strikes a boundary and is totally reflected. What is the intensity reflection coefficient?
100%
A sound wave with an intensity of 75 W/cm-squared, strikes a boundary and is totally reflected. What is the reflected intensity?
75 W/ cm-squared
Which of the following has the greatest attenuation and the slowest speed?
a.bone b.tendon
c. fat d. air
d
A sound wave hits a boundary between two media with different impedances. The angle of incidence is non-orthogonal. What happens to the sound?
some of the sound MAY be reflected
What is the meaning of a 9 dB change?
8 times bigger
