Question

# Please calculate the total transmission (I2/I1) of ultrasound intensity from medium 1 to medium 2 in...

Please calculate the total transmission (I2/I1) of ultrasound intensity from medium 1 to medium 2 in the following situations: (a) medium 1 directly contacts with medium 2. The acoustic impedences are noted in the figures below. (b) medium 3 is inserted between media 1 and 2. The acoustic impedence of medium 3 is 6.6 MRayls. (c) If the medium 3 is air with an impedence of 0.0004 MRayls. The attenuation in all the media is negnected.

a )

Accostic impedance is R = ( z2 - z1 / z2 + z1 )2

R + T = 1

T = 1 - R

T = 1 - ( z2 - z1 / z2 + z1 )2

T = 4 z2z1 / ( z2 + z1 )2

T = 4 X 1.65 X 26.4 / ( 1.65 + 26.4 )2

T = 0.22

b )

T1 = I3 / I1

= 4 X 6.6 X 26.4 / ( 6.6 + 26.4 )2

I3 = 0.64 I1

T2 = 4 X 1.65 X 6.6 / ( 1.65 + 6.6 )2

= 0.64

I2 / I3 = 0.64

I2 = 0.64 I3

I2 = 0.64 X 0.64 X I1

I2 / I1 = 0.41

c )

z3 = 0.0004 MRays

T1 = 4 X 4 X 10-4 X 26.4 / ( 4 X 10-4 + 26.4 )2

T1 = 1.5 X 10-5

T1 = I3 / I1 = 1.5 X 10-5

T2 = 4 X 1.65 X 4 X 10-4 / ( 1.65 + 4 X 10-4 )2

I2 / I3 = 9.7 X 10-4

I2 = 9.7 X 10-4 X I3

I2 = 9.7 X 10-4 X 1.5 X 10-5 X I1

I2 / I1 = 1.46 X 10-8

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