多普勒效应公式
f = f₀·(u+v₁cosα₁)/(u−v₂cosα₂)
u=声速, v₁=接收器速度, v₂=声源速度
靠近探头(Δf = f − f₀ > 0)
f = f₀·(u+v)/(u−v)
v = Δf·u / (2f₀+Δf)
k = Δf/(2f₀+Δf),v = k·u
远离探头(Δf = f₀ − f > 0)
f = f₀·(u−v)/(u+v)
v = Δf·u / (2f₀−Δf)
k'= Δf/(2f₀−Δf),v = k'·u
理论声速
u = 331.45×√(1+t/273.15) m/s
光电门测速
v = L/Δt = 0.050/Δt m/s
L=挡光片宽度5.0cm,Δt=两次挡光时差
k—v图斜率 = 声速u
v = u·k → 斜率即声速u