19-2 Traveling sound waves 1)Let us assume that the pistol is driven so that the density and pressure of air in the tube will vary as a sine function △p=△OnSn(kx-Ot) (19-1) △P=△PnSi(kx-ot) (192) 2)What's the relationship between Ap and AP From the definitions of bulk modulus(体模量/膨胀系数) (Eq(15-5)B=A and density p=m, when m is fixed,We have △ν △v △P △ν n=△phn B1) Let us assume that the pistol is driven so that the density and pressure of air in the tube will vary as a sine function. (19-1) (19-2) 2) What’s the relationship between and ? From the definitions of bulk modulus(体模量/膨胀系数) (Eq(15-5)) and density , when m is fixed, we have sin( k x t)  =  m − P P sin( kx t)  =  m − ( ) v v P B   = − v m  = B ρ P B P ρ v v ρ v v v m v v m ρ 0 2 Δ Δ ) Δ ( Δ Δ = − Δ = − = − = = 19-2 Traveling sound waves  P