Flashcards in Ch 1-4 8 Deck (56):
When one value increases, and so does the other value, the two values are said to be ___________.
The molecules vibrate in the same direction as the sound travels. I.e, sound waves.
The molecules vibrate at 90 degrees to the direction of energy travel. i.e. Water ripples
concentration of force
units: lb/sq inch, Pascals Pa
concentration of mass or weight
units: kg/cubic cm
measure of particle motion
units: cm, feet, miles
The distance of one wave cycle.
•The length of time it takes to complete one single cycle of sound or to one complete single wavelength.
Units: seconds, msec, hours – all units of time
The # of wave cycles per second.
1 cycle per second = 1 hertz Hz
The speed at which wave cycles travel.
(Sin Angle of Incidence)/(Sin Angle of Refraction)= c1/c2
Where c1 & c2 are the speeds of sound in the two mediums
Where P = excess pressure and
V=the particle velocity. OR
Z=P x c
Where c=speed of light
The dominant factor in attenuation (80%).
-conversion of sound to heat
Occurs at a boundary between 2 different media with different impedances.
-the sound bounces back (toward transducer)
z=P x V , measured in Rayls. (z=Density x Prop Speed)
Smooth surface that causes sound to bounce back toward the transducer.
Scatter returning in the same general direction as the transducer.
Interface has irregularities one wavelength or smaller.
Sound scatters symmetrically in all directions. Not related to incidence angle. Increase frequency, and increase this.
%R=Reflected Intesity/Incidence Intensity=((z2-z1)/(z2+z1))^2
Intensity Reflection Coefficient
90 degrees. (Porn)
not 90 degrees
a bending from a straight line or path or a change in direction of a wave travelling from one medium to another. Must have two things: an Oblique Incidence, and2 media with different propagation speeds. Related to the change in acoustic velocity. (If medium 2 is faster, then it will increase the transmit angle.
Sin (angle of transmit)/ sin (angle of incidence)=prop speed 2/prop speed 1
"bulk modulus." The extent to which a material cannot be compressed. To increase this will increase propagation speed.
Pulse, then listen for echo
Time from the start of one pulse to the end of the same pulse. THis can only be changed by changing the transducer.
% of the time that the system is transmitting a pulse and not "listening." Determined by the sound source.
# of pulses that occur in a single second(Hz/sec). Determined by the sound source.
Pulse Repetition Frequency (PRF)
Time from the start of a pulse to the start of the next pulse (includes "listening time").
Determined by the sound source. CAN be changed by the sonographer by changing the listening time.
Pulse Repetition Period (PRP)
The distance a pullse occupies in space. # of cycles in a pulse x wavelength. Determined by the sound source and the medium. Cannot be changed by the sonographer.
Increase freq, Increase this
Spatial Pulse Length
Weakening of a sound wave as it travels through media. Decrease in amplitude and decrease in intensity. Increase frequency and increase this
+3 Db doubles the sound
+10 dB ten times the sound
# value that expresses how different materials attenuate the sound beam per unit length (dB/cm). The average attenuation coefficient in soft tissue is 1/2 the transducer frequency.
The distance the sound beam travls when its intensity is reduced to 1/2 its original value.
The fraction of the original intensity after attenuation.
a peak aligns with a peak; increase in amplitude
a peak aligns with a trough; decrease in amplitude
Distance to Boundary = (go-return time x speed)/2
Every 13 microseconds of go-return time means the reflector is 1 cm deeper in the body
13 microsecond rule
when wave peaks and troughs continue to line up.
When troughs from one wave continually line up with the peaks from another wave.
The strength of the sound beam, maximum variation from the baseline (dB)
The rate that work is performed, rate of energy transfer in the entire beam. Measured in watts.
P=I x CS
P is proportional to Amplitude squared
Concentration of energy in certain areas of the sound beam
The highest intensity area or time of the sound beam
(Peak + low + medium)/3
Greatest at the center and in focal zone of the sound beam
Occurs with Time
Is greatest at the center of the beam
Related or proportional
Related, Proportional, Directly Proportional
As one value increases, the other value decreases.
The effects that are made on the human body
The thing that is creating the sound wave