Pressure-amplitude transmission coefficient
= Pressure-amplitude transmission coefficient
{title2=$t_p=2Z_2/(Z_1+Z_2)$}
The transmitted-to-incident compressional <pressure> or normal-stress amplitude ratio. At normal incidence, continuity of normal stress gives $t_p=1+r_p$, with <pressure-amplitude reflection coefficient> $r_p$. The transmitted <energy> fraction is $(Z_1/Z_2)t_p^2$, not $t_p^2$ alone.