Echography x = c/2t
Doppler shift fD = vf/c
Wave length l =c/f
Near field length N = D2/4l
Beam divergent sin(g) = 1.22l/D
Acoustic impedance Z = cr
Snell’s law sin(a)/sin(b) = c1/c2
Transmission coefficient RT = 2Z2/(z1 + Z2)
Reflection coefficient RR = 1 – RT = (Z2-Z1)/(Z2+Z1)
x Position, distance
c Sound speed
v Velocity of reflector
t Time
f Frequency
D Initial beam diameter
r Density
a, b Beam incident & refrected angle