Chapter 14 SOUND
Chapter 14 SOUND
Sound waves(声波) 波的几何描述: Wavefronts oit sourd Ray(波线) Wavefronts (波振面) Spherical waves Planar waves (球面波) 平面波)
Sound waves（声波） Planar waves （平面波） Wavefronts Ray（波线） S Wavefronts （波振面） Spherical waves （球面波） Point source 波的几何描述：
The speed of sound Sound waves are longitudinal mechanical waves that can travel through solids, liquids, or gases. The speed v of a sound wave in a medium( having bulk modulus b(容变弹性模量)and density p)is: B 纵波在媒质中的传播速度) △ Where: B p (Ap is change of pressure) △/
Sound waves are longitudinal mechanical waves that can travel through solids, liquids, or gases. The speed v of a sound wave in a medium (having bulk modulus B（容变弹性模量） and density ) is: B v = V V p B / Where: = − The speed of sound (p is change of pressure) （纵波在媒质中的传播速度）
interference S and s, are point sources, they are in phase, and same wavelength. when they travel P through point P, the path length difference: △L To relate phase difference to path length difference AL, we recall that a phase difference of 2nt rad corresponds to one wavelength. So: △L △L 2丌 2 h
interference S1 and s2 are point sources, they are in phase, and same wavelength. when they travel through point P, the path length difference: L= L2 -L1 s P 1 s2 L2 L1 To relate phase difference to path length difference L, we recall that a phase difference of 2 rad corresponds to one wavelength. So: L = 2 2 L =
△L (1)Whenφ=±2mπ,(m=0,1,2… p==2丌 we called fully constructive interference(相长王 YBE). The two waves are in phase at p △L=±m (2)Whenφ=±(2m+1)π,(m=0,1,2.) we called fully destructive interference(相消 王涉). The two waves are out of phase at P. △L=±(2m+1) Of course, two waves could produce intermediate interference when AL is other value
(1) When =±2m, (m=0, 1, 2….) we called fully constructive interference（相长干 涉）. The two waves are in phase at p. L = m (2) When =±(2m+1), (m=0, 1, 2….) we called fully destructive interference（相消 干涉）. The two waves are out of phase at P. 2 (2 1) L = m + Of course, two waves could produce intermediate interference when L is other value. 2 L =