Working out as follows
x= (20-6)/20 = 0.7
Fk = k / air specific heat ratio
Fk = 1.31/1.4
Fk = 0.94
xT = Fk * x
0.94 x 0.7 = 0.658
because xT < x = 0.658<0.7 flow through the valve is choked
Expansion factor Y
Y = 1 - x/( 3 x Fk x xT )
Y= 1- 0.7/( 3 x 0.94 x 0.658)
Y = 0.623...
Im unsure if I am on the correct track or have gone off on a tangent. Any help or guidance would be appreciated.
CMRR=20log10(Adiff/Acm)
120=20log10(10^5/Acm)
120/20=log10(100,000/Acm)
6=log10(100,000/Acm)
taking antilogs 1,000,000=100,000/Acm
Acm=100,000/1,000,000
Acm=0.1Max amplified...