Читать книгу Engineering Acoustics - Malcolm J. Crocker - Страница 114

1 We have that I = 1/4π(50)2 = 1/104 π (W/m2), then But for the directional source Lp(θ, ϕ) = 〈Lp〉S + DI(θ, ϕ), then assuming ρ c = 400 rayls, Lp(θ, ϕ) = 75 + 10 log 12 = 75 + 10 + 10 log 1.2 = 85.8 dB.

2 If the direction is away from the floor, then