Building Acoustics

60 Building acoustics either by using a complex wave number k' or a complex propagation coefficient Γ.^1 We shall introduce thes ...

Waves in fluid and solid media 61 0 x x. p v rv x t ρ ∂ ∂ =−+⋅ ∂∂ (3.24) Combining this equation with the corresponding one-dime ...

62 Building acoustics Figure 3.2 a) Intensity: power through a surface of area 1 m^2 normal to the direction of wave propagation ...

Waves in fluid and solid media 63 In this equation |ITn| is the absolute value of the normal sound intensity and I 0 is the refe ...

64 Building acoustics These two main types of process are denoted mechanical and aerodynamic/ hydrodynamic generated sound, resp ...

Waves in fluid and solid media 65 uuaa=׈ ejtω a r p(,)rt G frequency ω. The radial surface velocity of the sphere may then be w ...

66 Building acoustics if the wavelength is large in relation to the dimensions of the source (ka << 1) but for large value ...

Waves in fluid and solid media 67 +- h prt(,) G r (^1) r r 2 Figure 3.4 Dipole, two monopoles in opposite phase. An oscillating ...

68 Building acoustics Figure 3.5 A loudspeaker open at the back is a dipole source. a) No efficient radiation due to short dista ...

Waves in fluid and solid media 69 When this velocity is known, we may solve the first of these integrals. The second integral re ...

70 Building acoustics z y dS p(R, ) x R r q a θ φ φ z y dS p(R, ) x R r q a θ φ φ or (3.47) to find the sound pressure at a poin ...

Waves in fluid and solid media 71 3.8. The diameter 2⋅a is chosen equal to 250 mm and the sound pressure level distribution is s ...

72 Building acoustics force input. In connection with sound sources it will be useful to introduce yet another (mechanical) impe ...

Waves in fluid and solid media 73 ( r0)piston 01 [ 1 ] 11 11 (2 ) j (2 ) , 2J() 2H() where ( ) 1 and ( ). ZcSRkaXka x x Rx X x x ...

74 Building acoustics (^) () () 2 r0piston 0 1 (^28) j. ka^83 ka ka ZcSρ << π ⎡ ⎤ ≈+⎢ ⋅⎥ ⎢⎣ ⎥⎦ (3.59) This expression may ...

Waves in fluid and solid media 75 basis of the intensity in the two waves. As the intensity both in a plane and a spherical wave ...

76 Building acoustics Figure 3.10 Incident and reflected plane wave at a surface. By using Equations (3.9) and (3.17) we may exp ...

Waves in fluid and solid media 77 (^) g00 1 1 p p R Zc R ρ + = − (3.68) and furthermore g 00 g0 000 g g0 00 1 where. 1 p Z c ZZ ...

78 Building acoustics Figure 3.11 Absorption factor as a function of the normalised impedance components (Z = Zg/Z 0 ) of the bo ...

Waves in fluid and solid media 79 3.5.1.1 Sound pressure in front of a boundary surface Determination of the sound absorption fa ...