day 2 Flashcards
similar to the ordinary sounds we hear except that its frequency is higher than the range of human hearing
ultrasound
traveling variation in one or more quantities, such as pressure
wave
concentration of matter (mass per unit volume).
density
acoustic variables
period
wavelenght
amplitude
frequency
velocity
Regions of low pressure and density are called
rarefactions
regions of high pressure and density are called
compression
Sound is a mechanical compressional wave in which back-andforth particle motion is parallel to the direction of wave. Such a wave is called
longitudinal wave
The up-and-down motion of a water surface is perpendicular
to the direction of wave travel. This type of wave is called
transverse wave
time that it takes for one cycle to
occur
period
length of space that one cycle takes up. It is the length of a cycle from “front” to “back.”
wavelength
measurement of how often something happens
frequency
one complete variation in pressure or other acoustic variable
cycle
number of times it is
repeated in 1 second is
called
frequency
number of cycles in a wave that occur in 1 second.
frequency
sound of a frequency too low for human hearing. less than 20 Hz
infrasound
sound of a frequency too high for human hearing. 20000 Hz higher
ultrasound
It is determined by the medium, primarily its stiffness
propagation speed
resistance of a material to compression
stiffness
The average propagation speed of sound in tissues
1.54 mm/μs
Propagation in which speed depends on pressure and the shape of the wave changes
nonlinear propagation
even and odd
multiples of fundamental
frequency
harmonics
Any other wave shape contains additional frequencies that are even and odd multiples of the original frequency. The original frequency is called the
fundamental frequency
even and odd multiples of fundamental frequency
harmonics
The first working version of
marine SONAR (Sound Navigation
and Ranging) system was used
during the First World War to detect
enemy submarine
1916
early scanning technique required the patient to immersed in a bath of water in order to provide good transmission of sound wave into the body
early 1950’s
first contact compound B-Scanner (olive oil as lubricant) was developed
late 1950s
gray scale imaging was introduced, enabling the display of a wide range of echo amplitudes
1970s
real-time scanning systems were introduced. Dynamic Sonograhic
Information was available for
the first time
Mid 1970s
Doppler Technique is used
1980s
